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29967ef6 | 1 | //! A UTF-8–encoded, growable string. |
92a42be0 | 2 | //! |
29967ef6 XL |
3 | //! This module contains the [`String`] type, the [`ToString`] trait for |
4 | //! converting to strings, and several error types that may result from | |
5 | //! working with [`String`]s. | |
92a42be0 | 6 | //! |
9cc50fc6 SL |
7 | //! # Examples |
8 | //! | |
c30ab7b3 | 9 | //! There are multiple ways to create a new [`String`] from a string literal: |
9cc50fc6 | 10 | //! |
c30ab7b3 | 11 | //! ``` |
9cc50fc6 SL |
12 | //! let s = "Hello".to_string(); |
13 | //! | |
14 | //! let s = String::from("world"); | |
15 | //! let s: String = "also this".into(); | |
16 | //! ``` | |
17 | //! | |
c30ab7b3 | 18 | //! You can create a new [`String`] from an existing one by concatenating with |
9cc50fc6 SL |
19 | //! `+`: |
20 | //! | |
c30ab7b3 | 21 | //! ``` |
9cc50fc6 SL |
22 | //! let s = "Hello".to_string(); |
23 | //! | |
24 | //! let message = s + " world!"; | |
25 | //! ``` | |
26 | //! | |
3b2f2976 | 27 | //! If you have a vector of valid UTF-8 bytes, you can make a [`String`] out of |
9cc50fc6 SL |
28 | //! it. You can do the reverse too. |
29 | //! | |
c30ab7b3 | 30 | //! ``` |
9cc50fc6 SL |
31 | //! let sparkle_heart = vec![240, 159, 146, 150]; |
32 | //! | |
33 | //! // We know these bytes are valid, so we'll use `unwrap()`. | |
34 | //! let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); | |
35 | //! | |
36 | //! assert_eq!("💖", sparkle_heart); | |
37 | //! | |
38 | //! let bytes = sparkle_heart.into_bytes(); | |
39 | //! | |
40 | //! assert_eq!(bytes, [240, 159, 146, 150]); | |
41 | //! ``` | |
1a4d82fc | 42 | |
85aaf69f | 43 | #![stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 44 | |
83c7162d | 45 | use core::char::{decode_utf16, REPLACEMENT_CHARACTER}; |
1a4d82fc JJ |
46 | use core::fmt; |
47 | use core::hash; | |
9e0c209e | 48 | use core::iter::{FromIterator, FusedIterator}; |
9fa01778 | 49 | use core::ops::Bound::{Excluded, Included, Unbounded}; |
1b1a35ee | 50 | use core::ops::{self, Add, AddAssign, Index, IndexMut, Range, RangeBounds}; |
1a4d82fc | 51 | use core::ptr; |
6a06907d | 52 | use core::slice; |
dfeec247 | 53 | use core::str::{lossy, pattern::Pattern}; |
1a4d82fc | 54 | |
9fa01778 | 55 | use crate::borrow::{Cow, ToOwned}; |
9fa01778 | 56 | use crate::boxed::Box; |
dfeec247 XL |
57 | use crate::collections::TryReserveError; |
58 | use crate::str::{self, from_boxed_utf8_unchecked, Chars, FromStr, Utf8Error}; | |
9fa01778 | 59 | use crate::vec::Vec; |
1a4d82fc | 60 | |
29967ef6 | 61 | /// A UTF-8–encoded, growable string. |
92a42be0 SL |
62 | /// |
63 | /// The `String` type is the most common string type that has ownership over the | |
64 | /// contents of the string. It has a close relationship with its borrowed | |
65 | /// counterpart, the primitive [`str`]. | |
66 | /// | |
92a42be0 SL |
67 | /// # Examples |
68 | /// | |
3dfed10e XL |
69 | /// You can create a `String` from [a literal string][`str`] with [`String::from`]: |
70 | /// | |
71 | /// [`String::from`]: From::from | |
92a42be0 SL |
72 | /// |
73 | /// ``` | |
74 | /// let hello = String::from("Hello, world!"); | |
75 | /// ``` | |
76 | /// | |
cc61c64b XL |
77 | /// You can append a [`char`] to a `String` with the [`push`] method, and |
78 | /// append a [`&str`] with the [`push_str`] method: | |
92a42be0 SL |
79 | /// |
80 | /// ``` | |
81 | /// let mut hello = String::from("Hello, "); | |
82 | /// | |
83 | /// hello.push('w'); | |
84 | /// hello.push_str("orld!"); | |
85 | /// ``` | |
86 | /// | |
3dfed10e XL |
87 | /// [`push`]: String::push |
88 | /// [`push_str`]: String::push_str | |
92a42be0 SL |
89 | /// |
90 | /// If you have a vector of UTF-8 bytes, you can create a `String` from it with | |
cc61c64b | 91 | /// the [`from_utf8`] method: |
92a42be0 SL |
92 | /// |
93 | /// ``` | |
94 | /// // some bytes, in a vector | |
95 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
96 | /// | |
97 | /// // We know these bytes are valid, so we'll use `unwrap()`. | |
98 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); | |
99 | /// | |
100 | /// assert_eq!("💖", sparkle_heart); | |
101 | /// ``` | |
102 | /// | |
3dfed10e | 103 | /// [`from_utf8`]: String::from_utf8 |
92a42be0 SL |
104 | /// |
105 | /// # UTF-8 | |
106 | /// | |
107 | /// `String`s are always valid UTF-8. This has a few implications, the first of | |
108 | /// which is that if you need a non-UTF-8 string, consider [`OsString`]. It is | |
109 | /// similar, but without the UTF-8 constraint. The second implication is that | |
110 | /// you cannot index into a `String`: | |
111 | /// | |
041b39d2 | 112 | /// ```compile_fail,E0277 |
92a42be0 SL |
113 | /// let s = "hello"; |
114 | /// | |
115 | /// println!("The first letter of s is {}", s[0]); // ERROR!!! | |
116 | /// ``` | |
117 | /// | |
54a0048b | 118 | /// [`OsString`]: ../../std/ffi/struct.OsString.html |
92a42be0 SL |
119 | /// |
120 | /// Indexing is intended to be a constant-time operation, but UTF-8 encoding | |
9e0c209e | 121 | /// does not allow us to do this. Furthermore, it's not clear what sort of |
92a42be0 | 122 | /// thing the index should return: a byte, a codepoint, or a grapheme cluster. |
cc61c64b | 123 | /// The [`bytes`] and [`chars`] methods return iterators over the first |
92a42be0 SL |
124 | /// two, respectively. |
125 | /// | |
3dfed10e XL |
126 | /// [`bytes`]: str::bytes |
127 | /// [`chars`]: str::chars | |
92a42be0 SL |
128 | /// |
129 | /// # Deref | |
130 | /// | |
131 | /// `String`s implement [`Deref`]`<Target=str>`, and so inherit all of [`str`]'s | |
3b2f2976 | 132 | /// methods. In addition, this means that you can pass a `String` to a |
92a42be0 SL |
133 | /// function which takes a [`&str`] by using an ampersand (`&`): |
134 | /// | |
135 | /// ``` | |
136 | /// fn takes_str(s: &str) { } | |
137 | /// | |
138 | /// let s = String::from("Hello"); | |
139 | /// | |
140 | /// takes_str(&s); | |
141 | /// ``` | |
142 | /// | |
92a42be0 SL |
143 | /// This will create a [`&str`] from the `String` and pass it in. This |
144 | /// conversion is very inexpensive, and so generally, functions will accept | |
3b2f2976 XL |
145 | /// [`&str`]s as arguments unless they need a `String` for some specific |
146 | /// reason. | |
147 | /// | |
148 | /// In certain cases Rust doesn't have enough information to make this | |
149 | /// conversion, known as [`Deref`] coercion. In the following example a string | |
150 | /// slice [`&'a str`][`&str`] implements the trait `TraitExample`, and the function | |
151 | /// `example_func` takes anything that implements the trait. In this case Rust | |
152 | /// would need to make two implicit conversions, which Rust doesn't have the | |
153 | /// means to do. For that reason, the following example will not compile. | |
154 | /// | |
155 | /// ```compile_fail,E0277 | |
156 | /// trait TraitExample {} | |
157 | /// | |
158 | /// impl<'a> TraitExample for &'a str {} | |
92a42be0 | 159 | /// |
3b2f2976 XL |
160 | /// fn example_func<A: TraitExample>(example_arg: A) {} |
161 | /// | |
e74abb32 XL |
162 | /// let example_string = String::from("example_string"); |
163 | /// example_func(&example_string); | |
3b2f2976 XL |
164 | /// ``` |
165 | /// | |
166 | /// There are two options that would work instead. The first would be to | |
167 | /// change the line `example_func(&example_string);` to | |
168 | /// `example_func(example_string.as_str());`, using the method [`as_str()`] | |
169 | /// to explicitly extract the string slice containing the string. The second | |
170 | /// way changes `example_func(&example_string);` to | |
171 | /// `example_func(&*example_string);`. In this case we are dereferencing a | |
172 | /// `String` to a [`str`][`&str`], then referencing the [`str`][`&str`] back to | |
173 | /// [`&str`]. The second way is more idiomatic, however both work to do the | |
174 | /// conversion explicitly rather than relying on the implicit conversion. | |
92a42be0 SL |
175 | /// |
176 | /// # Representation | |
177 | /// | |
178 | /// A `String` is made up of three components: a pointer to some bytes, a | |
179 | /// length, and a capacity. The pointer points to an internal buffer `String` | |
180 | /// uses to store its data. The length is the number of bytes currently stored | |
181 | /// in the buffer, and the capacity is the size of the buffer in bytes. As such, | |
182 | /// the length will always be less than or equal to the capacity. | |
183 | /// | |
184 | /// This buffer is always stored on the heap. | |
185 | /// | |
cc61c64b | 186 | /// You can look at these with the [`as_ptr`], [`len`], and [`capacity`] |
92a42be0 SL |
187 | /// methods: |
188 | /// | |
189 | /// ``` | |
190 | /// use std::mem; | |
191 | /// | |
192 | /// let story = String::from("Once upon a time..."); | |
193 | /// | |
e74abb32 XL |
194 | // FIXME Update this when vec_into_raw_parts is stabilized |
195 | /// // Prevent automatically dropping the String's data | |
196 | /// let mut story = mem::ManuallyDrop::new(story); | |
197 | /// | |
198 | /// let ptr = story.as_mut_ptr(); | |
92a42be0 SL |
199 | /// let len = story.len(); |
200 | /// let capacity = story.capacity(); | |
201 | /// | |
a7813a04 | 202 | /// // story has nineteen bytes |
92a42be0 SL |
203 | /// assert_eq!(19, len); |
204 | /// | |
92a42be0 | 205 | /// // We can re-build a String out of ptr, len, and capacity. This is all |
7453a54e | 206 | /// // unsafe because we are responsible for making sure the components are |
92a42be0 | 207 | /// // valid: |
e74abb32 | 208 | /// let s = unsafe { String::from_raw_parts(ptr, len, capacity) } ; |
92a42be0 SL |
209 | /// |
210 | /// assert_eq!(String::from("Once upon a time..."), s); | |
211 | /// ``` | |
212 | /// | |
3dfed10e XL |
213 | /// [`as_ptr`]: str::as_ptr |
214 | /// [`len`]: String::len | |
215 | /// [`capacity`]: String::capacity | |
92a42be0 SL |
216 | /// |
217 | /// If a `String` has enough capacity, adding elements to it will not | |
218 | /// re-allocate. For example, consider this program: | |
219 | /// | |
220 | /// ``` | |
221 | /// let mut s = String::new(); | |
222 | /// | |
223 | /// println!("{}", s.capacity()); | |
224 | /// | |
225 | /// for _ in 0..5 { | |
226 | /// s.push_str("hello"); | |
227 | /// println!("{}", s.capacity()); | |
228 | /// } | |
229 | /// ``` | |
230 | /// | |
231 | /// This will output the following: | |
232 | /// | |
233 | /// ```text | |
234 | /// 0 | |
235 | /// 5 | |
236 | /// 10 | |
237 | /// 20 | |
238 | /// 20 | |
239 | /// 40 | |
240 | /// ``` | |
241 | /// | |
242 | /// At first, we have no memory allocated at all, but as we append to the | |
243 | /// string, it increases its capacity appropriately. If we instead use the | |
cc61c64b | 244 | /// [`with_capacity`] method to allocate the correct capacity initially: |
92a42be0 SL |
245 | /// |
246 | /// ``` | |
247 | /// let mut s = String::with_capacity(25); | |
248 | /// | |
249 | /// println!("{}", s.capacity()); | |
250 | /// | |
251 | /// for _ in 0..5 { | |
252 | /// s.push_str("hello"); | |
253 | /// println!("{}", s.capacity()); | |
254 | /// } | |
255 | /// ``` | |
256 | /// | |
3dfed10e | 257 | /// [`with_capacity`]: String::with_capacity |
92a42be0 SL |
258 | /// |
259 | /// We end up with a different output: | |
260 | /// | |
261 | /// ```text | |
262 | /// 25 | |
263 | /// 25 | |
264 | /// 25 | |
265 | /// 25 | |
266 | /// 25 | |
267 | /// 25 | |
268 | /// ``` | |
269 | /// | |
270 | /// Here, there's no need to allocate more memory inside the loop. | |
3b2f2976 | 271 | /// |
3dfed10e XL |
272 | /// [`str`]: prim@str |
273 | /// [`&str`]: prim@str | |
274 | /// [`Deref`]: core::ops::Deref | |
275 | /// [`as_str()`]: String::as_str | |
b039eaaf | 276 | #[derive(PartialOrd, Eq, Ord)] |
f9f354fc | 277 | #[cfg_attr(not(test), rustc_diagnostic_item = "string_type")] |
85aaf69f | 278 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
279 | pub struct String { |
280 | vec: Vec<u8>, | |
281 | } | |
282 | ||
92a42be0 SL |
283 | /// A possible error value when converting a `String` from a UTF-8 byte vector. |
284 | /// | |
cc61c64b | 285 | /// This type is the error type for the [`from_utf8`] method on [`String`]. It |
92a42be0 | 286 | /// is designed in such a way to carefully avoid reallocations: the |
cc61c64b | 287 | /// [`into_bytes`] method will give back the byte vector that was used in the |
92a42be0 SL |
288 | /// conversion attempt. |
289 | /// | |
3dfed10e XL |
290 | /// [`from_utf8`]: String::from_utf8 |
291 | /// [`into_bytes`]: FromUtf8Error::into_bytes | |
92a42be0 SL |
292 | /// |
293 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
294 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
295 | /// an analogue to `FromUtf8Error`, and you can get one from a `FromUtf8Error` | |
cc61c64b | 296 | /// through the [`utf8_error`] method. |
92a42be0 | 297 | /// |
3dfed10e XL |
298 | /// [`Utf8Error`]: core::str::Utf8Error |
299 | /// [`std::str`]: core::str | |
300 | /// [`&str`]: prim@str | |
301 | /// [`utf8_error`]: Self::utf8_error | |
92a42be0 SL |
302 | /// |
303 | /// # Examples | |
304 | /// | |
305 | /// Basic usage: | |
306 | /// | |
307 | /// ``` | |
308 | /// // some invalid bytes, in a vector | |
309 | /// let bytes = vec![0, 159]; | |
310 | /// | |
311 | /// let value = String::from_utf8(bytes); | |
312 | /// | |
313 | /// assert!(value.is_err()); | |
314 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
315 | /// ``` | |
85aaf69f | 316 | #[stable(feature = "rust1", since = "1.0.0")] |
74b04a01 | 317 | #[derive(Debug, Clone, PartialEq, Eq)] |
1a4d82fc JJ |
318 | pub struct FromUtf8Error { |
319 | bytes: Vec<u8>, | |
320 | error: Utf8Error, | |
321 | } | |
322 | ||
92a42be0 SL |
323 | /// A possible error value when converting a `String` from a UTF-16 byte slice. |
324 | /// | |
cc61c64b | 325 | /// This type is the error type for the [`from_utf16`] method on [`String`]. |
92a42be0 | 326 | /// |
3dfed10e | 327 | /// [`from_utf16`]: String::from_utf16 |
92a42be0 SL |
328 | /// # Examples |
329 | /// | |
330 | /// Basic usage: | |
331 | /// | |
332 | /// ``` | |
333 | /// // 𝄞mu<invalid>ic | |
334 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
335 | /// 0xD800, 0x0069, 0x0063]; | |
336 | /// | |
337 | /// assert!(String::from_utf16(v).is_err()); | |
338 | /// ``` | |
85aaf69f SL |
339 | #[stable(feature = "rust1", since = "1.0.0")] |
340 | #[derive(Debug)] | |
1a4d82fc JJ |
341 | pub struct FromUtf16Error(()); |
342 | ||
343 | impl String { | |
9cc50fc6 SL |
344 | /// Creates a new empty `String`. |
345 | /// | |
346 | /// Given that the `String` is empty, this will not allocate any initial | |
347 | /// buffer. While that means that this initial operation is very | |
0531ce1d | 348 | /// inexpensive, it may cause excessive allocation later when you add |
9cc50fc6 | 349 | /// data. If you have an idea of how much data the `String` will hold, |
cc61c64b | 350 | /// consider the [`with_capacity`] method to prevent excessive |
9cc50fc6 SL |
351 | /// re-allocation. |
352 | /// | |
3dfed10e | 353 | /// [`with_capacity`]: String::with_capacity |
1a4d82fc JJ |
354 | /// |
355 | /// # Examples | |
356 | /// | |
9cc50fc6 SL |
357 | /// Basic usage: |
358 | /// | |
1a4d82fc | 359 | /// ``` |
9cc50fc6 | 360 | /// let s = String::new(); |
1a4d82fc JJ |
361 | /// ``` |
362 | #[inline] | |
dfeec247 | 363 | #[rustc_const_stable(feature = "const_string_new", since = "1.32.0")] |
85aaf69f | 364 | #[stable(feature = "rust1", since = "1.0.0")] |
94b46f34 | 365 | pub const fn new() -> String { |
92a42be0 | 366 | String { vec: Vec::new() } |
1a4d82fc JJ |
367 | } |
368 | ||
9cc50fc6 SL |
369 | /// Creates a new empty `String` with a particular capacity. |
370 | /// | |
371 | /// `String`s have an internal buffer to hold their data. The capacity is | |
cc61c64b | 372 | /// the length of that buffer, and can be queried with the [`capacity`] |
9cc50fc6 SL |
373 | /// method. This method creates an empty `String`, but one with an initial |
374 | /// buffer that can hold `capacity` bytes. This is useful when you may be | |
375 | /// appending a bunch of data to the `String`, reducing the number of | |
376 | /// reallocations it needs to do. | |
377 | /// | |
3dfed10e | 378 | /// [`capacity`]: String::capacity |
9cc50fc6 SL |
379 | /// |
380 | /// If the given capacity is `0`, no allocation will occur, and this method | |
cc61c64b | 381 | /// is identical to the [`new`] method. |
9cc50fc6 | 382 | /// |
3dfed10e | 383 | /// [`new`]: String::new |
1a4d82fc JJ |
384 | /// |
385 | /// # Examples | |
386 | /// | |
9cc50fc6 SL |
387 | /// Basic usage: |
388 | /// | |
1a4d82fc JJ |
389 | /// ``` |
390 | /// let mut s = String::with_capacity(10); | |
92a42be0 SL |
391 | /// |
392 | /// // The String contains no chars, even though it has capacity for more | |
393 | /// assert_eq!(s.len(), 0); | |
394 | /// | |
395 | /// // These are all done without reallocating... | |
396 | /// let cap = s.capacity(); | |
a1dfa0c6 | 397 | /// for _ in 0..10 { |
92a42be0 SL |
398 | /// s.push('a'); |
399 | /// } | |
400 | /// | |
401 | /// assert_eq!(s.capacity(), cap); | |
402 | /// | |
74b04a01 | 403 | /// // ...but this may make the string reallocate |
92a42be0 | 404 | /// s.push('a'); |
1a4d82fc JJ |
405 | /// ``` |
406 | #[inline] | |
5869c6ff XL |
407 | #[doc(alias = "alloc")] |
408 | #[doc(alias = "malloc")] | |
85aaf69f SL |
409 | #[stable(feature = "rust1", since = "1.0.0")] |
410 | pub fn with_capacity(capacity: usize) -> String { | |
92a42be0 | 411 | String { vec: Vec::with_capacity(capacity) } |
1a4d82fc JJ |
412 | } |
413 | ||
c34b1796 AL |
414 | // HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is |
415 | // required for this method definition, is not available. Since we don't | |
416 | // require this method for testing purposes, I'll just stub it | |
417 | // NB see the slice::hack module in slice.rs for more information | |
418 | #[inline] | |
419 | #[cfg(test)] | |
420 | pub fn from_str(_: &str) -> String { | |
421 | panic!("not available with cfg(test)"); | |
1a4d82fc JJ |
422 | } |
423 | ||
b039eaaf SL |
424 | /// Converts a vector of bytes to a `String`. |
425 | /// | |
e74abb32 | 426 | /// A string ([`String`]) is made of bytes ([`u8`]), and a vector of bytes |
9cc50fc6 | 427 | /// ([`Vec<u8>`]) is made of bytes, so this function converts between the |
b039eaaf SL |
428 | /// two. Not all byte slices are valid `String`s, however: `String` |
429 | /// requires that it is valid UTF-8. `from_utf8()` checks to ensure that | |
430 | /// the bytes are valid UTF-8, and then does the conversion. | |
431 | /// | |
432 | /// If you are sure that the byte slice is valid UTF-8, and you don't want | |
433 | /// to incur the overhead of the validity check, there is an unsafe version | |
cc61c64b | 434 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 435 | /// but skips the check. |
b039eaaf | 436 | /// |
b039eaaf SL |
437 | /// This method will take care to not copy the vector, for efficiency's |
438 | /// sake. | |
439 | /// | |
3b2f2976 | 440 | /// If you need a [`&str`] instead of a `String`, consider |
cc61c64b | 441 | /// [`str::from_utf8`]. |
b039eaaf | 442 | /// |
e74abb32 | 443 | /// The inverse of this method is [`into_bytes`]. |
8bb4bdeb | 444 | /// |
7453a54e | 445 | /// # Errors |
1a4d82fc | 446 | /// |
3b2f2976 | 447 | /// Returns [`Err`] if the slice is not UTF-8 with a description as to why the |
b039eaaf | 448 | /// provided bytes are not UTF-8. The vector you moved in is also included. |
1a4d82fc JJ |
449 | /// |
450 | /// # Examples | |
451 | /// | |
b039eaaf SL |
452 | /// Basic usage: |
453 | /// | |
c34b1796 | 454 | /// ``` |
b039eaaf SL |
455 | /// // some bytes, in a vector |
456 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
457 | /// | |
92a42be0 | 458 | /// // We know these bytes are valid, so we'll use `unwrap()`. |
b039eaaf SL |
459 | /// let sparkle_heart = String::from_utf8(sparkle_heart).unwrap(); |
460 | /// | |
461 | /// assert_eq!("💖", sparkle_heart); | |
462 | /// ``` | |
463 | /// | |
464 | /// Incorrect bytes: | |
465 | /// | |
1a4d82fc | 466 | /// ``` |
b039eaaf SL |
467 | /// // some invalid bytes, in a vector |
468 | /// let sparkle_heart = vec![0, 159, 146, 150]; | |
469 | /// | |
470 | /// assert!(String::from_utf8(sparkle_heart).is_err()); | |
471 | /// ``` | |
472 | /// | |
9cc50fc6 SL |
473 | /// See the docs for [`FromUtf8Error`] for more details on what you can do |
474 | /// with this error. | |
b039eaaf | 475 | /// |
3dfed10e XL |
476 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
477 | /// [`Vec<u8>`]: crate::vec::Vec | |
478 | /// [`&str`]: prim@str | |
479 | /// [`into_bytes`]: String::into_bytes | |
1a4d82fc | 480 | #[inline] |
85aaf69f | 481 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 482 | pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> { |
85aaf69f | 483 | match str::from_utf8(&vec) { |
a1dfa0c6 | 484 | Ok(..) => Ok(String { vec }), |
dfeec247 | 485 | Err(e) => Err(FromUtf8Error { bytes: vec, error: e }), |
1a4d82fc JJ |
486 | } |
487 | } | |
488 | ||
7453a54e | 489 | /// Converts a slice of bytes to a string, including invalid characters. |
b039eaaf | 490 | /// |
7453a54e SL |
491 | /// Strings are made of bytes ([`u8`]), and a slice of bytes |
492 | /// ([`&[u8]`][byteslice]) is made of bytes, so this function converts | |
493 | /// between the two. Not all byte slices are valid strings, however: strings | |
494 | /// are required to be valid UTF-8. During this conversion, | |
9cc50fc6 | 495 | /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with |
b7449926 | 496 | /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: � |
b039eaaf | 497 | /// |
6a06907d | 498 | /// [byteslice]: prim@slice |
3dfed10e | 499 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER |
9cc50fc6 | 500 | /// |
b039eaaf SL |
501 | /// If you are sure that the byte slice is valid UTF-8, and you don't want |
502 | /// to incur the overhead of the conversion, there is an unsafe version | |
cc61c64b | 503 | /// of this function, [`from_utf8_unchecked`], which has the same behavior |
9cc50fc6 | 504 | /// but skips the checks. |
b039eaaf | 505 | /// |
3dfed10e | 506 | /// [`from_utf8_unchecked`]: String::from_utf8_unchecked |
b039eaaf | 507 | /// |
7453a54e SL |
508 | /// This function returns a [`Cow<'a, str>`]. If our byte slice is invalid |
509 | /// UTF-8, then we need to insert the replacement characters, which will | |
510 | /// change the size of the string, and hence, require a `String`. But if | |
511 | /// it's already valid UTF-8, we don't need a new allocation. This return | |
512 | /// type allows us to handle both cases. | |
b039eaaf | 513 | /// |
3dfed10e | 514 | /// [`Cow<'a, str>`]: crate::borrow::Cow |
1a4d82fc JJ |
515 | /// |
516 | /// # Examples | |
517 | /// | |
b039eaaf SL |
518 | /// Basic usage: |
519 | /// | |
c34b1796 | 520 | /// ``` |
b039eaaf SL |
521 | /// // some bytes, in a vector |
522 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
523 | /// | |
7453a54e | 524 | /// let sparkle_heart = String::from_utf8_lossy(&sparkle_heart); |
b039eaaf SL |
525 | /// |
526 | /// assert_eq!("💖", sparkle_heart); | |
527 | /// ``` | |
528 | /// | |
529 | /// Incorrect bytes: | |
530 | /// | |
531 | /// ``` | |
532 | /// // some invalid bytes | |
1a4d82fc JJ |
533 | /// let input = b"Hello \xF0\x90\x80World"; |
534 | /// let output = String::from_utf8_lossy(input); | |
b039eaaf SL |
535 | /// |
536 | /// assert_eq!("Hello �World", output); | |
1a4d82fc | 537 | /// ``` |
85aaf69f | 538 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 539 | pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> { |
041b39d2 | 540 | let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks(); |
1a4d82fc | 541 | |
041b39d2 XL |
542 | let (first_valid, first_broken) = if let Some(chunk) = iter.next() { |
543 | let lossy::Utf8LossyChunk { valid, broken } = chunk; | |
544 | if valid.len() == v.len() { | |
545 | debug_assert!(broken.is_empty()); | |
546 | return Cow::Borrowed(valid); | |
547 | } | |
548 | (valid, broken) | |
549 | } else { | |
550 | return Cow::Borrowed(""); | |
551 | }; | |
1a4d82fc | 552 | |
0731742a | 553 | const REPLACEMENT: &str = "\u{FFFD}"; |
1a4d82fc | 554 | |
041b39d2 XL |
555 | let mut res = String::with_capacity(v.len()); |
556 | res.push_str(first_valid); | |
557 | if !first_broken.is_empty() { | |
558 | res.push_str(REPLACEMENT); | |
1a4d82fc JJ |
559 | } |
560 | ||
041b39d2 XL |
561 | for lossy::Utf8LossyChunk { valid, broken } in iter { |
562 | res.push_str(valid); | |
563 | if !broken.is_empty() { | |
564 | res.push_str(REPLACEMENT); | |
1a4d82fc JJ |
565 | } |
566 | } | |
041b39d2 | 567 | |
1a4d82fc JJ |
568 | Cow::Owned(res) |
569 | } | |
570 | ||
29967ef6 | 571 | /// Decode a UTF-16–encoded vector `v` into a `String`, returning [`Err`] |
1a4d82fc JJ |
572 | /// if `v` contains any invalid data. |
573 | /// | |
574 | /// # Examples | |
575 | /// | |
9cc50fc6 SL |
576 | /// Basic usage: |
577 | /// | |
c34b1796 | 578 | /// ``` |
1a4d82fc | 579 | /// // 𝄞music |
92a42be0 SL |
580 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
581 | /// 0x0073, 0x0069, 0x0063]; | |
9cc50fc6 SL |
582 | /// assert_eq!(String::from("𝄞music"), |
583 | /// String::from_utf16(v).unwrap()); | |
1a4d82fc JJ |
584 | /// |
585 | /// // 𝄞mu<invalid>ic | |
92a42be0 SL |
586 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, |
587 | /// 0xD800, 0x0069, 0x0063]; | |
1a4d82fc JJ |
588 | /// assert!(String::from_utf16(v).is_err()); |
589 | /// ``` | |
85aaf69f | 590 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 591 | pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error> { |
a1dfa0c6 XL |
592 | // This isn't done via collect::<Result<_, _>>() for performance reasons. |
593 | // FIXME: the function can be simplified again when #48994 is closed. | |
594 | let mut ret = String::with_capacity(v.len()); | |
595 | for c in decode_utf16(v.iter().cloned()) { | |
596 | if let Ok(c) = c { | |
597 | ret.push(c); | |
598 | } else { | |
599 | return Err(FromUtf16Error(())); | |
600 | } | |
601 | } | |
602 | Ok(ret) | |
1a4d82fc JJ |
603 | } |
604 | ||
29967ef6 | 605 | /// Decode a UTF-16–encoded slice `v` into a `String`, replacing |
b7449926 | 606 | /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD]. |
1a4d82fc | 607 | /// |
ea8adc8c XL |
608 | /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`], |
609 | /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8 | |
610 | /// conversion requires a memory allocation. | |
611 | /// | |
3dfed10e XL |
612 | /// [`from_utf8_lossy`]: String::from_utf8_lossy |
613 | /// [`Cow<'a, str>`]: crate::borrow::Cow | |
614 | /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER | |
ea8adc8c | 615 | /// |
1a4d82fc JJ |
616 | /// # Examples |
617 | /// | |
9cc50fc6 SL |
618 | /// Basic usage: |
619 | /// | |
c34b1796 | 620 | /// ``` |
1a4d82fc JJ |
621 | /// // 𝄞mus<invalid>ic<invalid> |
622 | /// let v = &[0xD834, 0xDD1E, 0x006d, 0x0075, | |
623 | /// 0x0073, 0xDD1E, 0x0069, 0x0063, | |
624 | /// 0xD834]; | |
625 | /// | |
9cc50fc6 SL |
626 | /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"), |
627 | /// String::from_utf16_lossy(v)); | |
1a4d82fc | 628 | /// ``` |
85aaf69f SL |
629 | #[inline] |
630 | #[stable(feature = "rust1", since = "1.0.0")] | |
1a4d82fc | 631 | pub fn from_utf16_lossy(v: &[u16]) -> String { |
e9174d1e | 632 | decode_utf16(v.iter().cloned()).map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)).collect() |
1a4d82fc JJ |
633 | } |
634 | ||
e74abb32 XL |
635 | /// Decomposes a `String` into its raw components. |
636 | /// | |
637 | /// Returns the raw pointer to the underlying data, the length of | |
638 | /// the string (in bytes), and the allocated capacity of the data | |
639 | /// (in bytes). These are the same arguments in the same order as | |
640 | /// the arguments to [`from_raw_parts`]. | |
641 | /// | |
642 | /// After calling this function, the caller is responsible for the | |
643 | /// memory previously managed by the `String`. The only way to do | |
644 | /// this is to convert the raw pointer, length, and capacity back | |
645 | /// into a `String` with the [`from_raw_parts`] function, allowing | |
646 | /// the destructor to perform the cleanup. | |
647 | /// | |
3dfed10e | 648 | /// [`from_raw_parts`]: String::from_raw_parts |
e74abb32 XL |
649 | /// |
650 | /// # Examples | |
651 | /// | |
652 | /// ``` | |
653 | /// #![feature(vec_into_raw_parts)] | |
654 | /// let s = String::from("hello"); | |
655 | /// | |
656 | /// let (ptr, len, cap) = s.into_raw_parts(); | |
657 | /// | |
658 | /// let rebuilt = unsafe { String::from_raw_parts(ptr, len, cap) }; | |
659 | /// assert_eq!(rebuilt, "hello"); | |
660 | /// ``` | |
661 | #[unstable(feature = "vec_into_raw_parts", reason = "new API", issue = "65816")] | |
662 | pub fn into_raw_parts(self) -> (*mut u8, usize, usize) { | |
663 | self.vec.into_raw_parts() | |
664 | } | |
665 | ||
1a4d82fc JJ |
666 | /// Creates a new `String` from a length, capacity, and pointer. |
667 | /// | |
b039eaaf | 668 | /// # Safety |
c1a9b12d | 669 | /// |
9cc50fc6 SL |
670 | /// This is highly unsafe, due to the number of invariants that aren't |
671 | /// checked: | |
672 | /// | |
3dfed10e | 673 | /// * The memory at `buf` needs to have been previously allocated by the |
60c5eb7d | 674 | /// same allocator the standard library uses, with a required alignment of exactly 1. |
9cc50fc6 SL |
675 | /// * `length` needs to be less than or equal to `capacity`. |
676 | /// * `capacity` needs to be the correct value. | |
3dfed10e | 677 | /// * The first `length` bytes at `buf` need to be valid UTF-8. |
9cc50fc6 SL |
678 | /// |
679 | /// Violating these may cause problems like corrupting the allocator's | |
3b2f2976 | 680 | /// internal data structures. |
9cc50fc6 | 681 | /// |
3dfed10e | 682 | /// The ownership of `buf` is effectively transferred to the |
5bcae85e SL |
683 | /// `String` which may then deallocate, reallocate or change the |
684 | /// contents of memory pointed to by the pointer at will. Ensure | |
685 | /// that nothing else uses the pointer after calling this | |
686 | /// function. | |
687 | /// | |
9cc50fc6 SL |
688 | /// # Examples |
689 | /// | |
690 | /// Basic usage: | |
691 | /// | |
692 | /// ``` | |
693 | /// use std::mem; | |
694 | /// | |
695 | /// unsafe { | |
696 | /// let s = String::from("hello"); | |
e74abb32 XL |
697 | /// |
698 | // FIXME Update this when vec_into_raw_parts is stabilized | |
699 | /// // Prevent automatically dropping the String's data | |
700 | /// let mut s = mem::ManuallyDrop::new(s); | |
701 | /// | |
702 | /// let ptr = s.as_mut_ptr(); | |
9cc50fc6 SL |
703 | /// let len = s.len(); |
704 | /// let capacity = s.capacity(); | |
705 | /// | |
e74abb32 | 706 | /// let s = String::from_raw_parts(ptr, len, capacity); |
c34b1796 | 707 | /// |
9cc50fc6 SL |
708 | /// assert_eq!(String::from("hello"), s); |
709 | /// } | |
710 | /// ``` | |
1a4d82fc | 711 | #[inline] |
85aaf69f SL |
712 | #[stable(feature = "rust1", since = "1.0.0")] |
713 | pub unsafe fn from_raw_parts(buf: *mut u8, length: usize, capacity: usize) -> String { | |
f035d41b | 714 | unsafe { String { vec: Vec::from_raw_parts(buf, length, capacity) } } |
1a4d82fc JJ |
715 | } |
716 | ||
b039eaaf SL |
717 | /// Converts a vector of bytes to a `String` without checking that the |
718 | /// string contains valid UTF-8. | |
719 | /// | |
cc61c64b | 720 | /// See the safe version, [`from_utf8`], for more details. |
b039eaaf | 721 | /// |
3dfed10e | 722 | /// [`from_utf8`]: String::from_utf8 |
b039eaaf SL |
723 | /// |
724 | /// # Safety | |
725 | /// | |
9cc50fc6 SL |
726 | /// This function is unsafe because it does not check that the bytes passed |
727 | /// to it are valid UTF-8. If this constraint is violated, it may cause | |
728 | /// memory unsafety issues with future users of the `String`, as the rest of | |
729 | /// the standard library assumes that `String`s are valid UTF-8. | |
b039eaaf SL |
730 | /// |
731 | /// # Examples | |
732 | /// | |
733 | /// Basic usage: | |
734 | /// | |
735 | /// ``` | |
736 | /// // some bytes, in a vector | |
737 | /// let sparkle_heart = vec![240, 159, 146, 150]; | |
738 | /// | |
739 | /// let sparkle_heart = unsafe { | |
740 | /// String::from_utf8_unchecked(sparkle_heart) | |
741 | /// }; | |
742 | /// | |
743 | /// assert_eq!("💖", sparkle_heart); | |
744 | /// ``` | |
1a4d82fc | 745 | #[inline] |
85aaf69f | 746 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
747 | pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String { |
748 | String { vec: bytes } | |
749 | } | |
750 | ||
9cc50fc6 SL |
751 | /// Converts a `String` into a byte vector. |
752 | /// | |
753 | /// This consumes the `String`, so we do not need to copy its contents. | |
1a4d82fc JJ |
754 | /// |
755 | /// # Examples | |
756 | /// | |
9cc50fc6 SL |
757 | /// Basic usage: |
758 | /// | |
1a4d82fc | 759 | /// ``` |
62682a34 | 760 | /// let s = String::from("hello"); |
1a4d82fc | 761 | /// let bytes = s.into_bytes(); |
9cc50fc6 SL |
762 | /// |
763 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]); | |
1a4d82fc JJ |
764 | /// ``` |
765 | #[inline] | |
85aaf69f | 766 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
767 | pub fn into_bytes(self) -> Vec<u8> { |
768 | self.vec | |
769 | } | |
770 | ||
b7449926 | 771 | /// Extracts a string slice containing the entire `String`. |
ea8adc8c XL |
772 | /// |
773 | /// # Examples | |
774 | /// | |
775 | /// Basic usage: | |
776 | /// | |
777 | /// ``` | |
778 | /// let s = String::from("foo"); | |
779 | /// | |
780 | /// assert_eq!("foo", s.as_str()); | |
781 | /// ``` | |
c34b1796 | 782 | #[inline] |
9cc50fc6 | 783 | #[stable(feature = "string_as_str", since = "1.7.0")] |
c34b1796 AL |
784 | pub fn as_str(&self) -> &str { |
785 | self | |
786 | } | |
787 | ||
ea8adc8c XL |
788 | /// Converts a `String` into a mutable string slice. |
789 | /// | |
790 | /// # Examples | |
791 | /// | |
792 | /// Basic usage: | |
793 | /// | |
794 | /// ``` | |
ea8adc8c XL |
795 | /// let mut s = String::from("foobar"); |
796 | /// let s_mut_str = s.as_mut_str(); | |
797 | /// | |
798 | /// s_mut_str.make_ascii_uppercase(); | |
799 | /// | |
800 | /// assert_eq!("FOOBAR", s_mut_str); | |
801 | /// ``` | |
9cc50fc6 SL |
802 | #[inline] |
803 | #[stable(feature = "string_as_str", since = "1.7.0")] | |
804 | pub fn as_mut_str(&mut self) -> &mut str { | |
805 | self | |
806 | } | |
807 | ||
808 | /// Appends a given string slice onto the end of this `String`. | |
1a4d82fc JJ |
809 | /// |
810 | /// # Examples | |
811 | /// | |
9cc50fc6 SL |
812 | /// Basic usage: |
813 | /// | |
1a4d82fc | 814 | /// ``` |
62682a34 | 815 | /// let mut s = String::from("foo"); |
9cc50fc6 | 816 | /// |
1a4d82fc | 817 | /// s.push_str("bar"); |
9cc50fc6 SL |
818 | /// |
819 | /// assert_eq!("foobar", s); | |
1a4d82fc JJ |
820 | /// ``` |
821 | #[inline] | |
85aaf69f | 822 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 823 | pub fn push_str(&mut self, string: &str) { |
92a42be0 | 824 | self.vec.extend_from_slice(string.as_bytes()) |
1a4d82fc JJ |
825 | } |
826 | ||
9cc50fc6 | 827 | /// Returns this `String`'s capacity, in bytes. |
1a4d82fc JJ |
828 | /// |
829 | /// # Examples | |
830 | /// | |
9cc50fc6 SL |
831 | /// Basic usage: |
832 | /// | |
1a4d82fc JJ |
833 | /// ``` |
834 | /// let s = String::with_capacity(10); | |
9cc50fc6 | 835 | /// |
1a4d82fc JJ |
836 | /// assert!(s.capacity() >= 10); |
837 | /// ``` | |
838 | #[inline] | |
85aaf69f SL |
839 | #[stable(feature = "rust1", since = "1.0.0")] |
840 | pub fn capacity(&self) -> usize { | |
1a4d82fc JJ |
841 | self.vec.capacity() |
842 | } | |
843 | ||
9cc50fc6 SL |
844 | /// Ensures that this `String`'s capacity is at least `additional` bytes |
845 | /// larger than its length. | |
846 | /// | |
847 | /// The capacity may be increased by more than `additional` bytes if it | |
848 | /// chooses, to prevent frequent reallocations. | |
849 | /// | |
cc61c64b | 850 | /// If you do not want this "at least" behavior, see the [`reserve_exact`] |
9cc50fc6 SL |
851 | /// method. |
852 | /// | |
1a4d82fc JJ |
853 | /// # Panics |
854 | /// | |
3b2f2976 XL |
855 | /// Panics if the new capacity overflows [`usize`]. |
856 | /// | |
3dfed10e | 857 | /// [`reserve_exact`]: String::reserve_exact |
1a4d82fc JJ |
858 | /// |
859 | /// # Examples | |
860 | /// | |
9cc50fc6 SL |
861 | /// Basic usage: |
862 | /// | |
1a4d82fc JJ |
863 | /// ``` |
864 | /// let mut s = String::new(); | |
9cc50fc6 | 865 | /// |
1a4d82fc | 866 | /// s.reserve(10); |
9cc50fc6 | 867 | /// |
1a4d82fc JJ |
868 | /// assert!(s.capacity() >= 10); |
869 | /// ``` | |
9cc50fc6 SL |
870 | /// |
871 | /// This may not actually increase the capacity: | |
872 | /// | |
873 | /// ``` | |
874 | /// let mut s = String::with_capacity(10); | |
875 | /// s.push('a'); | |
876 | /// s.push('b'); | |
877 | /// | |
878 | /// // s now has a length of 2 and a capacity of 10 | |
879 | /// assert_eq!(2, s.len()); | |
880 | /// assert_eq!(10, s.capacity()); | |
881 | /// | |
882 | /// // Since we already have an extra 8 capacity, calling this... | |
883 | /// s.reserve(8); | |
884 | /// | |
885 | /// // ... doesn't actually increase. | |
886 | /// assert_eq!(10, s.capacity()); | |
887 | /// ``` | |
1a4d82fc | 888 | #[inline] |
85aaf69f SL |
889 | #[stable(feature = "rust1", since = "1.0.0")] |
890 | pub fn reserve(&mut self, additional: usize) { | |
1a4d82fc JJ |
891 | self.vec.reserve(additional) |
892 | } | |
893 | ||
9cc50fc6 SL |
894 | /// Ensures that this `String`'s capacity is `additional` bytes |
895 | /// larger than its length. | |
1a4d82fc | 896 | /// |
cc61c64b | 897 | /// Consider using the [`reserve`] method unless you absolutely know |
9cc50fc6 SL |
898 | /// better than the allocator. |
899 | /// | |
3dfed10e | 900 | /// [`reserve`]: String::reserve |
1a4d82fc JJ |
901 | /// |
902 | /// # Panics | |
903 | /// | |
85aaf69f | 904 | /// Panics if the new capacity overflows `usize`. |
1a4d82fc JJ |
905 | /// |
906 | /// # Examples | |
907 | /// | |
9cc50fc6 SL |
908 | /// Basic usage: |
909 | /// | |
1a4d82fc JJ |
910 | /// ``` |
911 | /// let mut s = String::new(); | |
9cc50fc6 | 912 | /// |
62682a34 | 913 | /// s.reserve_exact(10); |
9cc50fc6 | 914 | /// |
1a4d82fc JJ |
915 | /// assert!(s.capacity() >= 10); |
916 | /// ``` | |
9cc50fc6 SL |
917 | /// |
918 | /// This may not actually increase the capacity: | |
919 | /// | |
920 | /// ``` | |
921 | /// let mut s = String::with_capacity(10); | |
922 | /// s.push('a'); | |
923 | /// s.push('b'); | |
924 | /// | |
925 | /// // s now has a length of 2 and a capacity of 10 | |
926 | /// assert_eq!(2, s.len()); | |
927 | /// assert_eq!(10, s.capacity()); | |
928 | /// | |
929 | /// // Since we already have an extra 8 capacity, calling this... | |
930 | /// s.reserve_exact(8); | |
931 | /// | |
932 | /// // ... doesn't actually increase. | |
933 | /// assert_eq!(10, s.capacity()); | |
934 | /// ``` | |
1a4d82fc | 935 | #[inline] |
85aaf69f SL |
936 | #[stable(feature = "rust1", since = "1.0.0")] |
937 | pub fn reserve_exact(&mut self, additional: usize) { | |
1a4d82fc JJ |
938 | self.vec.reserve_exact(additional) |
939 | } | |
940 | ||
0531ce1d XL |
941 | /// Tries to reserve capacity for at least `additional` more elements to be inserted |
942 | /// in the given `String`. The collection may reserve more space to avoid | |
943 | /// frequent reallocations. After calling `reserve`, capacity will be | |
944 | /// greater than or equal to `self.len() + additional`. Does nothing if | |
945 | /// capacity is already sufficient. | |
946 | /// | |
947 | /// # Errors | |
948 | /// | |
949 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
950 | /// is returned. | |
951 | /// | |
952 | /// # Examples | |
953 | /// | |
954 | /// ``` | |
955 | /// #![feature(try_reserve)] | |
e1599b0c | 956 | /// use std::collections::TryReserveError; |
0531ce1d | 957 | /// |
e1599b0c | 958 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
959 | /// let mut output = String::new(); |
960 | /// | |
961 | /// // Pre-reserve the memory, exiting if we can't | |
962 | /// output.try_reserve(data.len())?; | |
963 | /// | |
964 | /// // Now we know this can't OOM in the middle of our complex work | |
965 | /// output.push_str(data); | |
966 | /// | |
967 | /// Ok(output) | |
968 | /// } | |
969 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
970 | /// ``` | |
dfeec247 | 971 | #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] |
e1599b0c | 972 | pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { |
0531ce1d XL |
973 | self.vec.try_reserve(additional) |
974 | } | |
975 | ||
5869c6ff | 976 | /// Tries to reserve the minimum capacity for exactly `additional` more elements to |
0531ce1d XL |
977 | /// be inserted in the given `String`. After calling `reserve_exact`, |
978 | /// capacity will be greater than or equal to `self.len() + additional`. | |
979 | /// Does nothing if the capacity is already sufficient. | |
980 | /// | |
981 | /// Note that the allocator may give the collection more space than it | |
9fa01778 | 982 | /// requests. Therefore, capacity can not be relied upon to be precisely |
0531ce1d XL |
983 | /// minimal. Prefer `reserve` if future insertions are expected. |
984 | /// | |
985 | /// # Errors | |
986 | /// | |
987 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
988 | /// is returned. | |
989 | /// | |
990 | /// # Examples | |
991 | /// | |
992 | /// ``` | |
993 | /// #![feature(try_reserve)] | |
e1599b0c | 994 | /// use std::collections::TryReserveError; |
0531ce1d | 995 | /// |
e1599b0c | 996 | /// fn process_data(data: &str) -> Result<String, TryReserveError> { |
0531ce1d XL |
997 | /// let mut output = String::new(); |
998 | /// | |
999 | /// // Pre-reserve the memory, exiting if we can't | |
1000 | /// output.try_reserve(data.len())?; | |
1001 | /// | |
1002 | /// // Now we know this can't OOM in the middle of our complex work | |
1003 | /// output.push_str(data); | |
1004 | /// | |
1005 | /// Ok(output) | |
1006 | /// } | |
1007 | /// # process_data("rust").expect("why is the test harness OOMing on 4 bytes?"); | |
1008 | /// ``` | |
dfeec247 XL |
1009 | #[unstable(feature = "try_reserve", reason = "new API", issue = "48043")] |
1010 | pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { | |
0531ce1d XL |
1011 | self.vec.try_reserve_exact(additional) |
1012 | } | |
1013 | ||
9cc50fc6 | 1014 | /// Shrinks the capacity of this `String` to match its length. |
1a4d82fc JJ |
1015 | /// |
1016 | /// # Examples | |
1017 | /// | |
9cc50fc6 SL |
1018 | /// Basic usage: |
1019 | /// | |
1a4d82fc | 1020 | /// ``` |
62682a34 | 1021 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1022 | /// |
1a4d82fc JJ |
1023 | /// s.reserve(100); |
1024 | /// assert!(s.capacity() >= 100); | |
9cc50fc6 | 1025 | /// |
1a4d82fc | 1026 | /// s.shrink_to_fit(); |
9cc50fc6 | 1027 | /// assert_eq!(3, s.capacity()); |
1a4d82fc JJ |
1028 | /// ``` |
1029 | #[inline] | |
85aaf69f | 1030 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1031 | pub fn shrink_to_fit(&mut self) { |
1032 | self.vec.shrink_to_fit() | |
1033 | } | |
1034 | ||
0531ce1d XL |
1035 | /// Shrinks the capacity of this `String` with a lower bound. |
1036 | /// | |
1037 | /// The capacity will remain at least as large as both the length | |
1038 | /// and the supplied value. | |
1039 | /// | |
5869c6ff | 1040 | /// If the current capacity is less than the lower limit, this is a no-op. |
0531ce1d XL |
1041 | /// |
1042 | /// # Examples | |
1043 | /// | |
1044 | /// ``` | |
1045 | /// #![feature(shrink_to)] | |
1046 | /// let mut s = String::from("foo"); | |
1047 | /// | |
1048 | /// s.reserve(100); | |
1049 | /// assert!(s.capacity() >= 100); | |
1050 | /// | |
1051 | /// s.shrink_to(10); | |
1052 | /// assert!(s.capacity() >= 10); | |
1053 | /// s.shrink_to(0); | |
1054 | /// assert!(s.capacity() >= 3); | |
1055 | /// ``` | |
1056 | #[inline] | |
dfeec247 | 1057 | #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] |
0531ce1d XL |
1058 | pub fn shrink_to(&mut self, min_capacity: usize) { |
1059 | self.vec.shrink_to(min_capacity) | |
1060 | } | |
1061 | ||
3b2f2976 XL |
1062 | /// Appends the given [`char`] to the end of this `String`. |
1063 | /// | |
1a4d82fc JJ |
1064 | /// # Examples |
1065 | /// | |
9cc50fc6 SL |
1066 | /// Basic usage: |
1067 | /// | |
1a4d82fc | 1068 | /// ``` |
62682a34 | 1069 | /// let mut s = String::from("abc"); |
9cc50fc6 | 1070 | /// |
1a4d82fc JJ |
1071 | /// s.push('1'); |
1072 | /// s.push('2'); | |
1073 | /// s.push('3'); | |
9cc50fc6 SL |
1074 | /// |
1075 | /// assert_eq!("abc123", s); | |
1a4d82fc JJ |
1076 | /// ``` |
1077 | #[inline] | |
85aaf69f | 1078 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1079 | pub fn push(&mut self, ch: char) { |
62682a34 SL |
1080 | match ch.len_utf8() { |
1081 | 1 => self.vec.push(ch as u8), | |
32a655c1 | 1082 | _ => self.vec.extend_from_slice(ch.encode_utf8(&mut [0; 4]).as_bytes()), |
1a4d82fc JJ |
1083 | } |
1084 | } | |
1085 | ||
9cc50fc6 | 1086 | /// Returns a byte slice of this `String`'s contents. |
1a4d82fc | 1087 | /// |
8bb4bdeb XL |
1088 | /// The inverse of this method is [`from_utf8`]. |
1089 | /// | |
3dfed10e | 1090 | /// [`from_utf8`]: String::from_utf8 |
8bb4bdeb | 1091 | /// |
1a4d82fc JJ |
1092 | /// # Examples |
1093 | /// | |
9cc50fc6 SL |
1094 | /// Basic usage: |
1095 | /// | |
1a4d82fc | 1096 | /// ``` |
62682a34 | 1097 | /// let s = String::from("hello"); |
9cc50fc6 SL |
1098 | /// |
1099 | /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes()); | |
1a4d82fc JJ |
1100 | /// ``` |
1101 | #[inline] | |
85aaf69f SL |
1102 | #[stable(feature = "rust1", since = "1.0.0")] |
1103 | pub fn as_bytes(&self) -> &[u8] { | |
1104 | &self.vec | |
1a4d82fc JJ |
1105 | } |
1106 | ||
9cc50fc6 | 1107 | /// Shortens this `String` to the specified length. |
1a4d82fc | 1108 | /// |
a7813a04 XL |
1109 | /// If `new_len` is greater than the string's current length, this has no |
1110 | /// effect. | |
1111 | /// | |
8bb4bdeb XL |
1112 | /// Note that this method has no effect on the allocated capacity |
1113 | /// of the string | |
1114 | /// | |
1a4d82fc JJ |
1115 | /// # Panics |
1116 | /// | |
a7813a04 | 1117 | /// Panics if `new_len` does not lie on a [`char`] boundary. |
9cc50fc6 | 1118 | /// |
1a4d82fc JJ |
1119 | /// # Examples |
1120 | /// | |
9cc50fc6 SL |
1121 | /// Basic usage: |
1122 | /// | |
1a4d82fc | 1123 | /// ``` |
62682a34 | 1124 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1125 | /// |
1a4d82fc | 1126 | /// s.truncate(2); |
9cc50fc6 SL |
1127 | /// |
1128 | /// assert_eq!("he", s); | |
1a4d82fc JJ |
1129 | /// ``` |
1130 | #[inline] | |
85aaf69f SL |
1131 | #[stable(feature = "rust1", since = "1.0.0")] |
1132 | pub fn truncate(&mut self, new_len: usize) { | |
a7813a04 XL |
1133 | if new_len <= self.len() { |
1134 | assert!(self.is_char_boundary(new_len)); | |
1135 | self.vec.truncate(new_len) | |
1136 | } | |
1a4d82fc JJ |
1137 | } |
1138 | ||
1139 | /// Removes the last character from the string buffer and returns it. | |
9cc50fc6 | 1140 | /// |
3b2f2976 XL |
1141 | /// Returns [`None`] if this `String` is empty. |
1142 | /// | |
1a4d82fc JJ |
1143 | /// # Examples |
1144 | /// | |
9cc50fc6 SL |
1145 | /// Basic usage: |
1146 | /// | |
1a4d82fc | 1147 | /// ``` |
62682a34 | 1148 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1149 | /// |
1a4d82fc JJ |
1150 | /// assert_eq!(s.pop(), Some('o')); |
1151 | /// assert_eq!(s.pop(), Some('o')); | |
1152 | /// assert_eq!(s.pop(), Some('f')); | |
9cc50fc6 | 1153 | /// |
1a4d82fc JJ |
1154 | /// assert_eq!(s.pop(), None); |
1155 | /// ``` | |
1156 | #[inline] | |
85aaf69f | 1157 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1158 | pub fn pop(&mut self) -> Option<char> { |
ff7c6d11 | 1159 | let ch = self.chars().rev().next()?; |
54a0048b | 1160 | let newlen = self.len() - ch.len_utf8(); |
1a4d82fc | 1161 | unsafe { |
54a0048b | 1162 | self.vec.set_len(newlen); |
1a4d82fc JJ |
1163 | } |
1164 | Some(ch) | |
1165 | } | |
1166 | ||
3b2f2976 | 1167 | /// Removes a [`char`] from this `String` at a byte position and returns it. |
1a4d82fc | 1168 | /// |
3dfed10e | 1169 | /// This is an *O*(*n*) operation, as it requires copying every element in the |
1a4d82fc JJ |
1170 | /// buffer. |
1171 | /// | |
1172 | /// # Panics | |
1173 | /// | |
9cc50fc6 SL |
1174 | /// Panics if `idx` is larger than or equal to the `String`'s length, |
1175 | /// or if it does not lie on a [`char`] boundary. | |
1176 | /// | |
1a4d82fc JJ |
1177 | /// # Examples |
1178 | /// | |
9cc50fc6 SL |
1179 | /// Basic usage: |
1180 | /// | |
1a4d82fc | 1181 | /// ``` |
62682a34 | 1182 | /// let mut s = String::from("foo"); |
9cc50fc6 | 1183 | /// |
1a4d82fc JJ |
1184 | /// assert_eq!(s.remove(0), 'f'); |
1185 | /// assert_eq!(s.remove(1), 'o'); | |
1186 | /// assert_eq!(s.remove(0), 'o'); | |
1187 | /// ``` | |
85aaf69f SL |
1188 | #[inline] |
1189 | #[stable(feature = "rust1", since = "1.0.0")] | |
1190 | pub fn remove(&mut self, idx: usize) -> char { | |
54a0048b SL |
1191 | let ch = match self[idx..].chars().next() { |
1192 | Some(ch) => ch, | |
1193 | None => panic!("cannot remove a char from the end of a string"), | |
1194 | }; | |
1a4d82fc | 1195 | |
c34b1796 | 1196 | let next = idx + ch.len_utf8(); |
54a0048b | 1197 | let len = self.len(); |
1a4d82fc | 1198 | unsafe { |
dfeec247 | 1199 | ptr::copy(self.vec.as_ptr().add(next), self.vec.as_mut_ptr().add(idx), len - next); |
1a4d82fc JJ |
1200 | self.vec.set_len(len - (next - idx)); |
1201 | } | |
1202 | ch | |
1203 | } | |
1204 | ||
6a06907d XL |
1205 | /// Remove all matches of pattern `pat` in the `String`. |
1206 | /// | |
1207 | /// # Examples | |
1208 | /// | |
1209 | /// ``` | |
1210 | /// #![feature(string_remove_matches)] | |
1211 | /// let mut s = String::from("Trees are not green, the sky is not blue."); | |
1212 | /// s.remove_matches("not "); | |
1213 | /// assert_eq!("Trees are green, the sky is blue.", s); | |
1214 | /// ``` | |
1215 | /// | |
1216 | /// Matches will be detected and removed iteratively, so in cases where | |
1217 | /// patterns overlap, only the first pattern will be removed: | |
1218 | /// | |
1219 | /// ``` | |
1220 | /// #![feature(string_remove_matches)] | |
1221 | /// let mut s = String::from("banana"); | |
1222 | /// s.remove_matches("ana"); | |
1223 | /// assert_eq!("bna", s); | |
1224 | /// ``` | |
1225 | #[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")] | |
1226 | pub fn remove_matches<'a, P>(&'a mut self, pat: P) | |
1227 | where | |
1228 | P: for<'x> Pattern<'x>, | |
1229 | { | |
1230 | use core::str::pattern::Searcher; | |
1231 | ||
1232 | let matches = { | |
1233 | let mut searcher = pat.into_searcher(self); | |
1234 | let mut matches = Vec::new(); | |
1235 | ||
1236 | while let Some(m) = searcher.next_match() { | |
1237 | matches.push(m); | |
1238 | } | |
1239 | ||
1240 | matches | |
1241 | }; | |
1242 | ||
1243 | let len = self.len(); | |
1244 | let mut shrunk_by = 0; | |
1245 | ||
1246 | // SAFETY: start and end will be on utf8 byte boundaries per | |
1247 | // the Searcher docs | |
1248 | unsafe { | |
1249 | for (start, end) in matches { | |
1250 | ptr::copy( | |
1251 | self.vec.as_mut_ptr().add(end - shrunk_by), | |
1252 | self.vec.as_mut_ptr().add(start - shrunk_by), | |
1253 | len - end, | |
1254 | ); | |
1255 | shrunk_by += end - start; | |
1256 | } | |
1257 | self.vec.set_len(len - shrunk_by); | |
1258 | } | |
1259 | } | |
1260 | ||
3b2f2976 XL |
1261 | /// Retains only the characters specified by the predicate. |
1262 | /// | |
1263 | /// In other words, remove all characters `c` such that `f(c)` returns `false`. | |
48663c56 XL |
1264 | /// This method operates in place, visiting each character exactly once in the |
1265 | /// original order, and preserves the order of the retained characters. | |
3b2f2976 XL |
1266 | /// |
1267 | /// # Examples | |
1268 | /// | |
1269 | /// ``` | |
3b2f2976 XL |
1270 | /// let mut s = String::from("f_o_ob_ar"); |
1271 | /// | |
1272 | /// s.retain(|c| c != '_'); | |
1273 | /// | |
1274 | /// assert_eq!(s, "foobar"); | |
1275 | /// ``` | |
48663c56 XL |
1276 | /// |
1277 | /// The exact order may be useful for tracking external state, like an index. | |
1278 | /// | |
1279 | /// ``` | |
1280 | /// let mut s = String::from("abcde"); | |
1281 | /// let keep = [false, true, true, false, true]; | |
1282 | /// let mut i = 0; | |
1283 | /// s.retain(|_| (keep[i], i += 1).0); | |
1284 | /// assert_eq!(s, "bce"); | |
1285 | /// ``` | |
3b2f2976 | 1286 | #[inline] |
0531ce1d | 1287 | #[stable(feature = "string_retain", since = "1.26.0")] |
3b2f2976 | 1288 | pub fn retain<F>(&mut self, mut f: F) |
dfeec247 XL |
1289 | where |
1290 | F: FnMut(char) -> bool, | |
3b2f2976 XL |
1291 | { |
1292 | let len = self.len(); | |
1293 | let mut del_bytes = 0; | |
1294 | let mut idx = 0; | |
1295 | ||
29967ef6 XL |
1296 | unsafe { |
1297 | self.vec.set_len(0); | |
1298 | } | |
1299 | ||
3b2f2976 | 1300 | while idx < len { |
dfeec247 | 1301 | let ch = unsafe { self.get_unchecked(idx..len).chars().next().unwrap() }; |
3b2f2976 XL |
1302 | let ch_len = ch.len_utf8(); |
1303 | ||
1304 | if !f(ch) { | |
1305 | del_bytes += ch_len; | |
1306 | } else if del_bytes > 0 { | |
1307 | unsafe { | |
dfeec247 XL |
1308 | ptr::copy( |
1309 | self.vec.as_ptr().add(idx), | |
1310 | self.vec.as_mut_ptr().add(idx - del_bytes), | |
1311 | ch_len, | |
1312 | ); | |
3b2f2976 XL |
1313 | } |
1314 | } | |
1315 | ||
1316 | // Point idx to the next char | |
1317 | idx += ch_len; | |
1318 | } | |
1319 | ||
29967ef6 XL |
1320 | unsafe { |
1321 | self.vec.set_len(len - del_bytes); | |
3b2f2976 XL |
1322 | } |
1323 | } | |
1324 | ||
9cc50fc6 | 1325 | /// Inserts a character into this `String` at a byte position. |
1a4d82fc | 1326 | /// |
3dfed10e | 1327 | /// This is an *O*(*n*) operation as it requires copying every element in the |
1a4d82fc JJ |
1328 | /// buffer. |
1329 | /// | |
1330 | /// # Panics | |
1331 | /// | |
9cc50fc6 SL |
1332 | /// Panics if `idx` is larger than the `String`'s length, or if it does not |
1333 | /// lie on a [`char`] boundary. | |
1334 | /// | |
9cc50fc6 SL |
1335 | /// # Examples |
1336 | /// | |
1337 | /// Basic usage: | |
1338 | /// | |
1339 | /// ``` | |
1340 | /// let mut s = String::with_capacity(3); | |
1341 | /// | |
1342 | /// s.insert(0, 'f'); | |
1343 | /// s.insert(1, 'o'); | |
1344 | /// s.insert(2, 'o'); | |
1345 | /// | |
1346 | /// assert_eq!("foo", s); | |
1347 | /// ``` | |
85aaf69f SL |
1348 | #[inline] |
1349 | #[stable(feature = "rust1", since = "1.0.0")] | |
1350 | pub fn insert(&mut self, idx: usize, ch: char) { | |
1a4d82fc | 1351 | assert!(self.is_char_boundary(idx)); |
c30ab7b3 SL |
1352 | let mut bits = [0; 4]; |
1353 | let bits = ch.encode_utf8(&mut bits).as_bytes(); | |
5bcae85e SL |
1354 | |
1355 | unsafe { | |
c30ab7b3 | 1356 | self.insert_bytes(idx, bits); |
5bcae85e SL |
1357 | } |
1358 | } | |
1359 | ||
1360 | unsafe fn insert_bytes(&mut self, idx: usize, bytes: &[u8]) { | |
1361 | let len = self.len(); | |
1362 | let amt = bytes.len(); | |
54a0048b | 1363 | self.vec.reserve(amt); |
1a4d82fc | 1364 | |
f035d41b XL |
1365 | unsafe { |
1366 | ptr::copy(self.vec.as_ptr().add(idx), self.vec.as_mut_ptr().add(idx + amt), len - idx); | |
1367 | ptr::copy(bytes.as_ptr(), self.vec.as_mut_ptr().add(idx), amt); | |
1368 | self.vec.set_len(len + amt); | |
1369 | } | |
5bcae85e SL |
1370 | } |
1371 | ||
1372 | /// Inserts a string slice into this `String` at a byte position. | |
1373 | /// | |
3dfed10e | 1374 | /// This is an *O*(*n*) operation as it requires copying every element in the |
5bcae85e SL |
1375 | /// buffer. |
1376 | /// | |
1377 | /// # Panics | |
1378 | /// | |
1379 | /// Panics if `idx` is larger than the `String`'s length, or if it does not | |
1380 | /// lie on a [`char`] boundary. | |
1381 | /// | |
5bcae85e SL |
1382 | /// # Examples |
1383 | /// | |
1384 | /// Basic usage: | |
1385 | /// | |
1386 | /// ``` | |
5bcae85e SL |
1387 | /// let mut s = String::from("bar"); |
1388 | /// | |
1389 | /// s.insert_str(0, "foo"); | |
1390 | /// | |
1391 | /// assert_eq!("foobar", s); | |
1392 | /// ``` | |
1393 | #[inline] | |
32a655c1 | 1394 | #[stable(feature = "insert_str", since = "1.16.0")] |
5bcae85e | 1395 | pub fn insert_str(&mut self, idx: usize, string: &str) { |
5bcae85e SL |
1396 | assert!(self.is_char_boundary(idx)); |
1397 | ||
1a4d82fc | 1398 | unsafe { |
5bcae85e | 1399 | self.insert_bytes(idx, string.as_bytes()); |
1a4d82fc JJ |
1400 | } |
1401 | } | |
1402 | ||
9cc50fc6 | 1403 | /// Returns a mutable reference to the contents of this `String`. |
1a4d82fc | 1404 | /// |
9cc50fc6 SL |
1405 | /// # Safety |
1406 | /// | |
1407 | /// This function is unsafe because it does not check that the bytes passed | |
1408 | /// to it are valid UTF-8. If this constraint is violated, it may cause | |
1409 | /// memory unsafety issues with future users of the `String`, as the rest of | |
1410 | /// the standard library assumes that `String`s are valid UTF-8. | |
1a4d82fc JJ |
1411 | /// |
1412 | /// # Examples | |
1413 | /// | |
9cc50fc6 SL |
1414 | /// Basic usage: |
1415 | /// | |
1a4d82fc | 1416 | /// ``` |
62682a34 | 1417 | /// let mut s = String::from("hello"); |
9cc50fc6 | 1418 | /// |
1a4d82fc JJ |
1419 | /// unsafe { |
1420 | /// let vec = s.as_mut_vec(); | |
9cc50fc6 SL |
1421 | /// assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]); |
1422 | /// | |
1a4d82fc JJ |
1423 | /// vec.reverse(); |
1424 | /// } | |
c34b1796 | 1425 | /// assert_eq!(s, "olleh"); |
1a4d82fc | 1426 | /// ``` |
85aaf69f SL |
1427 | #[inline] |
1428 | #[stable(feature = "rust1", since = "1.0.0")] | |
1429 | pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8> { | |
1a4d82fc JJ |
1430 | &mut self.vec |
1431 | } | |
1432 | ||
60c5eb7d XL |
1433 | /// Returns the length of this `String`, in bytes, not [`char`]s or |
1434 | /// graphemes. In other words, it may not be what a human considers the | |
1435 | /// length of the string. | |
1a4d82fc JJ |
1436 | /// |
1437 | /// # Examples | |
1438 | /// | |
9cc50fc6 SL |
1439 | /// Basic usage: |
1440 | /// | |
1a4d82fc | 1441 | /// ``` |
9cc50fc6 | 1442 | /// let a = String::from("foo"); |
1a4d82fc | 1443 | /// assert_eq!(a.len(), 3); |
60c5eb7d XL |
1444 | /// |
1445 | /// let fancy_f = String::from("ƒoo"); | |
1446 | /// assert_eq!(fancy_f.len(), 4); | |
1447 | /// assert_eq!(fancy_f.chars().count(), 3); | |
1a4d82fc | 1448 | /// ``` |
5869c6ff | 1449 | #[doc(alias = "length")] |
1a4d82fc | 1450 | #[inline] |
85aaf69f | 1451 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1452 | pub fn len(&self) -> usize { |
1453 | self.vec.len() | |
1454 | } | |
1a4d82fc | 1455 | |
9fa01778 | 1456 | /// Returns `true` if this `String` has a length of zero, and `false` otherwise. |
1a4d82fc JJ |
1457 | /// |
1458 | /// # Examples | |
1459 | /// | |
9cc50fc6 SL |
1460 | /// Basic usage: |
1461 | /// | |
1a4d82fc JJ |
1462 | /// ``` |
1463 | /// let mut v = String::new(); | |
1464 | /// assert!(v.is_empty()); | |
9cc50fc6 | 1465 | /// |
1a4d82fc JJ |
1466 | /// v.push('a'); |
1467 | /// assert!(!v.is_empty()); | |
1468 | /// ``` | |
85aaf69f SL |
1469 | #[inline] |
1470 | #[stable(feature = "rust1", since = "1.0.0")] | |
92a42be0 SL |
1471 | pub fn is_empty(&self) -> bool { |
1472 | self.len() == 0 | |
1473 | } | |
1a4d82fc | 1474 | |
fc512014 | 1475 | /// Splits the string into two at the given byte index. |
476ff2be | 1476 | /// |
8bb4bdeb XL |
1477 | /// Returns a newly allocated `String`. `self` contains bytes `[0, at)`, and |
1478 | /// the returned `String` contains bytes `[at, len)`. `at` must be on the | |
1479 | /// boundary of a UTF-8 code point. | |
476ff2be | 1480 | /// |
8bb4bdeb | 1481 | /// Note that the capacity of `self` does not change. |
476ff2be SL |
1482 | /// |
1483 | /// # Panics | |
1484 | /// | |
8bb4bdeb | 1485 | /// Panics if `at` is not on a `UTF-8` code point boundary, or if it is beyond the last |
476ff2be SL |
1486 | /// code point of the string. |
1487 | /// | |
1488 | /// # Examples | |
1489 | /// | |
1490 | /// ``` | |
476ff2be SL |
1491 | /// # fn main() { |
1492 | /// let mut hello = String::from("Hello, World!"); | |
1493 | /// let world = hello.split_off(7); | |
1494 | /// assert_eq!(hello, "Hello, "); | |
1495 | /// assert_eq!(world, "World!"); | |
1496 | /// # } | |
1497 | /// ``` | |
1498 | #[inline] | |
32a655c1 | 1499 | #[stable(feature = "string_split_off", since = "1.16.0")] |
ba9703b0 | 1500 | #[must_use = "use `.truncate()` if you don't need the other half"] |
8bb4bdeb XL |
1501 | pub fn split_off(&mut self, at: usize) -> String { |
1502 | assert!(self.is_char_boundary(at)); | |
1503 | let other = self.vec.split_off(at); | |
476ff2be SL |
1504 | unsafe { String::from_utf8_unchecked(other) } |
1505 | } | |
1506 | ||
9cc50fc6 SL |
1507 | /// Truncates this `String`, removing all contents. |
1508 | /// | |
1509 | /// While this means the `String` will have a length of zero, it does not | |
1510 | /// touch its capacity. | |
1a4d82fc JJ |
1511 | /// |
1512 | /// # Examples | |
1513 | /// | |
9cc50fc6 SL |
1514 | /// Basic usage: |
1515 | /// | |
1a4d82fc | 1516 | /// ``` |
9cc50fc6 SL |
1517 | /// let mut s = String::from("foo"); |
1518 | /// | |
1a4d82fc | 1519 | /// s.clear(); |
9cc50fc6 | 1520 | /// |
1a4d82fc | 1521 | /// assert!(s.is_empty()); |
9cc50fc6 SL |
1522 | /// assert_eq!(0, s.len()); |
1523 | /// assert_eq!(3, s.capacity()); | |
1a4d82fc JJ |
1524 | /// ``` |
1525 | #[inline] | |
85aaf69f | 1526 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1527 | pub fn clear(&mut self) { |
1528 | self.vec.clear() | |
1529 | } | |
d9579d0f | 1530 | |
b7449926 XL |
1531 | /// Creates a draining iterator that removes the specified range in the `String` |
1532 | /// and yields the removed `chars`. | |
9cc50fc6 SL |
1533 | /// |
1534 | /// Note: The element range is removed even if the iterator is not | |
1535 | /// consumed until the end. | |
d9579d0f AL |
1536 | /// |
1537 | /// # Panics | |
1538 | /// | |
9cc50fc6 SL |
1539 | /// Panics if the starting point or end point do not lie on a [`char`] |
1540 | /// boundary, or if they're out of bounds. | |
1541 | /// | |
d9579d0f AL |
1542 | /// # Examples |
1543 | /// | |
9cc50fc6 SL |
1544 | /// Basic usage: |
1545 | /// | |
d9579d0f | 1546 | /// ``` |
d9579d0f AL |
1547 | /// let mut s = String::from("α is alpha, β is beta"); |
1548 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1549 | /// | |
1550 | /// // Remove the range up until the β from the string | |
1551 | /// let t: String = s.drain(..beta_offset).collect(); | |
1552 | /// assert_eq!(t, "α is alpha, "); | |
1553 | /// assert_eq!(s, "β is beta"); | |
1554 | /// | |
1555 | /// // A full range clears the string | |
1556 | /// s.drain(..); | |
1557 | /// assert_eq!(s, ""); | |
1558 | /// ``` | |
92a42be0 | 1559 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1560 | pub fn drain<R>(&mut self, range: R) -> Drain<'_> |
dfeec247 XL |
1561 | where |
1562 | R: RangeBounds<usize>, | |
92a42be0 | 1563 | { |
d9579d0f AL |
1564 | // Memory safety |
1565 | // | |
1566 | // The String version of Drain does not have the memory safety issues | |
1567 | // of the vector version. The data is just plain bytes. | |
1568 | // Because the range removal happens in Drop, if the Drain iterator is leaked, | |
1569 | // the removal will not happen. | |
6a06907d | 1570 | let Range { start, end } = slice::range(range, ..self.len()); |
1b1a35ee XL |
1571 | assert!(self.is_char_boundary(start)); |
1572 | assert!(self.is_char_boundary(end)); | |
d9579d0f AL |
1573 | |
1574 | // Take out two simultaneous borrows. The &mut String won't be accessed | |
1575 | // until iteration is over, in Drop. | |
1576 | let self_ptr = self as *mut _; | |
6a06907d | 1577 | // SAFETY: `slice::range` and `is_char_boundary` do the appropriate bounds checks. |
1b1a35ee | 1578 | let chars_iter = unsafe { self.get_unchecked(start..end) }.chars(); |
d9579d0f | 1579 | |
dfeec247 | 1580 | Drain { start, end, iter: chars_iter, string: self_ptr } |
d9579d0f | 1581 | } |
c1a9b12d | 1582 | |
83c7162d | 1583 | /// Removes the specified range in the string, |
ea8adc8c XL |
1584 | /// and replaces it with the given string. |
1585 | /// The given string doesn't need to be the same length as the range. | |
7cac9316 | 1586 | /// |
7cac9316 XL |
1587 | /// # Panics |
1588 | /// | |
1589 | /// Panics if the starting point or end point do not lie on a [`char`] | |
1590 | /// boundary, or if they're out of bounds. | |
1591 | /// | |
7cac9316 XL |
1592 | /// # Examples |
1593 | /// | |
1594 | /// Basic usage: | |
1595 | /// | |
1596 | /// ``` | |
7cac9316 XL |
1597 | /// let mut s = String::from("α is alpha, β is beta"); |
1598 | /// let beta_offset = s.find('β').unwrap_or(s.len()); | |
1599 | /// | |
1600 | /// // Replace the range up until the β from the string | |
83c7162d | 1601 | /// s.replace_range(..beta_offset, "Α is capital alpha; "); |
7cac9316 XL |
1602 | /// assert_eq!(s, "Α is capital alpha; β is beta"); |
1603 | /// ``` | |
83c7162d XL |
1604 | #[stable(feature = "splice", since = "1.27.0")] |
1605 | pub fn replace_range<R>(&mut self, range: R, replace_with: &str) | |
dfeec247 XL |
1606 | where |
1607 | R: RangeBounds<usize>, | |
7cac9316 XL |
1608 | { |
1609 | // Memory safety | |
1610 | // | |
83c7162d | 1611 | // Replace_range does not have the memory safety issues of a vector Splice. |
7cac9316 | 1612 | // of the vector version. The data is just plain bytes. |
ea8adc8c | 1613 | |
5869c6ff XL |
1614 | // WARNING: Inlining this variable would be unsound (#81138) |
1615 | let start = range.start_bound(); | |
1616 | match start { | |
dfeec247 XL |
1617 | Included(&n) => assert!(self.is_char_boundary(n)), |
1618 | Excluded(&n) => assert!(self.is_char_boundary(n + 1)), | |
1619 | Unbounded => {} | |
7cac9316 | 1620 | }; |
5869c6ff XL |
1621 | // WARNING: Inlining this variable would be unsound (#81138) |
1622 | let end = range.end_bound(); | |
1623 | match end { | |
dfeec247 XL |
1624 | Included(&n) => assert!(self.is_char_boundary(n + 1)), |
1625 | Excluded(&n) => assert!(self.is_char_boundary(n)), | |
1626 | Unbounded => {} | |
7cac9316 XL |
1627 | }; |
1628 | ||
5869c6ff XL |
1629 | // Using `range` again would be unsound (#81138) |
1630 | // We assume the bounds reported by `range` remain the same, but | |
1631 | // an adversarial implementation could change between calls | |
1632 | unsafe { self.as_mut_vec() }.splice((start, end), replace_with.bytes()); | |
7cac9316 XL |
1633 | } |
1634 | ||
3b2f2976 | 1635 | /// Converts this `String` into a [`Box`]`<`[`str`]`>`. |
9cc50fc6 SL |
1636 | /// |
1637 | /// This will drop any excess capacity. | |
1638 | /// | |
3dfed10e | 1639 | /// [`str`]: prim@str |
3b2f2976 | 1640 | /// |
9cc50fc6 SL |
1641 | /// # Examples |
1642 | /// | |
1643 | /// Basic usage: | |
1644 | /// | |
1645 | /// ``` | |
1646 | /// let s = String::from("hello"); | |
c1a9b12d | 1647 | /// |
9cc50fc6 SL |
1648 | /// let b = s.into_boxed_str(); |
1649 | /// ``` | |
e9174d1e | 1650 | #[stable(feature = "box_str", since = "1.4.0")] |
83c7162d | 1651 | #[inline] |
e9174d1e | 1652 | pub fn into_boxed_str(self) -> Box<str> { |
c1a9b12d | 1653 | let slice = self.vec.into_boxed_slice(); |
041b39d2 | 1654 | unsafe { from_boxed_utf8_unchecked(slice) } |
c1a9b12d | 1655 | } |
1a4d82fc JJ |
1656 | } |
1657 | ||
1658 | impl FromUtf8Error { | |
cc61c64b XL |
1659 | /// Returns a slice of [`u8`]s bytes that were attempted to convert to a `String`. |
1660 | /// | |
1661 | /// # Examples | |
1662 | /// | |
1663 | /// Basic usage: | |
1664 | /// | |
1665 | /// ``` | |
cc61c64b XL |
1666 | /// // some invalid bytes, in a vector |
1667 | /// let bytes = vec![0, 159]; | |
1668 | /// | |
1669 | /// let value = String::from_utf8(bytes); | |
1670 | /// | |
1671 | /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes()); | |
1672 | /// ``` | |
0531ce1d | 1673 | #[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")] |
cc61c64b XL |
1674 | pub fn as_bytes(&self) -> &[u8] { |
1675 | &self.bytes[..] | |
1676 | } | |
1677 | ||
92a42be0 SL |
1678 | /// Returns the bytes that were attempted to convert to a `String`. |
1679 | /// | |
1680 | /// This method is carefully constructed to avoid allocation. It will | |
1681 | /// consume the error, moving out the bytes, so that a copy of the bytes | |
1682 | /// does not need to be made. | |
1683 | /// | |
1684 | /// # Examples | |
1685 | /// | |
1686 | /// Basic usage: | |
1687 | /// | |
1688 | /// ``` | |
1689 | /// // some invalid bytes, in a vector | |
1690 | /// let bytes = vec![0, 159]; | |
1691 | /// | |
1692 | /// let value = String::from_utf8(bytes); | |
1693 | /// | |
1694 | /// assert_eq!(vec![0, 159], value.unwrap_err().into_bytes()); | |
1695 | /// ``` | |
85aaf69f | 1696 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1697 | pub fn into_bytes(self) -> Vec<u8> { |
1698 | self.bytes | |
1699 | } | |
1a4d82fc | 1700 | |
92a42be0 SL |
1701 | /// Fetch a `Utf8Error` to get more details about the conversion failure. |
1702 | /// | |
1703 | /// The [`Utf8Error`] type provided by [`std::str`] represents an error that may | |
1704 | /// occur when converting a slice of [`u8`]s to a [`&str`]. In this sense, it's | |
1705 | /// an analogue to `FromUtf8Error`. See its documentation for more details | |
1706 | /// on using it. | |
1707 | /// | |
3dfed10e XL |
1708 | /// [`std::str`]: core::str |
1709 | /// [`&str`]: prim@str | |
92a42be0 SL |
1710 | /// |
1711 | /// # Examples | |
1712 | /// | |
1713 | /// Basic usage: | |
1714 | /// | |
1715 | /// ``` | |
1716 | /// // some invalid bytes, in a vector | |
1717 | /// let bytes = vec![0, 159]; | |
1718 | /// | |
1719 | /// let error = String::from_utf8(bytes).unwrap_err().utf8_error(); | |
1720 | /// | |
1721 | /// // the first byte is invalid here | |
1722 | /// assert_eq!(1, error.valid_up_to()); | |
1723 | /// ``` | |
85aaf69f | 1724 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1725 | pub fn utf8_error(&self) -> Utf8Error { |
1726 | self.error | |
1727 | } | |
1a4d82fc JJ |
1728 | } |
1729 | ||
85aaf69f SL |
1730 | #[stable(feature = "rust1", since = "1.0.0")] |
1731 | impl fmt::Display for FromUtf8Error { | |
9fa01778 | 1732 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1733 | fmt::Display::fmt(&self.error, f) |
1a4d82fc JJ |
1734 | } |
1735 | } | |
1736 | ||
85aaf69f SL |
1737 | #[stable(feature = "rust1", since = "1.0.0")] |
1738 | impl fmt::Display for FromUtf16Error { | |
9fa01778 | 1739 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 1740 | fmt::Display::fmt("invalid utf-16: lone surrogate found", f) |
1a4d82fc JJ |
1741 | } |
1742 | } | |
1743 | ||
b039eaaf SL |
1744 | #[stable(feature = "rust1", since = "1.0.0")] |
1745 | impl Clone for String { | |
1746 | fn clone(&self) -> Self { | |
1747 | String { vec: self.vec.clone() } | |
1748 | } | |
1749 | ||
1750 | fn clone_from(&mut self, source: &Self) { | |
1751 | self.vec.clone_from(&source.vec); | |
1752 | } | |
1753 | } | |
1754 | ||
85aaf69f | 1755 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1756 | impl FromIterator<char> for String { |
54a0048b | 1757 | fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String { |
1a4d82fc | 1758 | let mut buf = String::new(); |
54a0048b | 1759 | buf.extend(iter); |
1a4d82fc JJ |
1760 | buf |
1761 | } | |
1762 | } | |
1763 | ||
8bb4bdeb XL |
1764 | #[stable(feature = "string_from_iter_by_ref", since = "1.17.0")] |
1765 | impl<'a> FromIterator<&'a char> for String { | |
1766 | fn from_iter<I: IntoIterator<Item = &'a char>>(iter: I) -> String { | |
1767 | let mut buf = String::new(); | |
1768 | buf.extend(iter); | |
1769 | buf | |
1770 | } | |
1771 | } | |
1772 | ||
85aaf69f | 1773 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1774 | impl<'a> FromIterator<&'a str> for String { |
54a0048b | 1775 | fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String { |
e9174d1e | 1776 | let mut buf = String::new(); |
54a0048b | 1777 | buf.extend(iter); |
e9174d1e SL |
1778 | buf |
1779 | } | |
1780 | } | |
1781 | ||
1782 | #[stable(feature = "extend_string", since = "1.4.0")] | |
1783 | impl FromIterator<String> for String { | |
54a0048b | 1784 | fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String { |
0731742a XL |
1785 | let mut iterator = iter.into_iter(); |
1786 | ||
1787 | // Because we're iterating over `String`s, we can avoid at least | |
1788 | // one allocation by getting the first string from the iterator | |
1789 | // and appending to it all the subsequent strings. | |
1790 | match iterator.next() { | |
1791 | None => String::new(), | |
1792 | Some(mut buf) => { | |
1793 | buf.extend(iterator); | |
1794 | buf | |
1795 | } | |
1796 | } | |
1a4d82fc JJ |
1797 | } |
1798 | } | |
1799 | ||
f035d41b XL |
1800 | #[stable(feature = "box_str2", since = "1.45.0")] |
1801 | impl FromIterator<Box<str>> for String { | |
1802 | fn from_iter<I: IntoIterator<Item = Box<str>>>(iter: I) -> String { | |
1803 | let mut buf = String::new(); | |
1804 | buf.extend(iter); | |
1805 | buf | |
1806 | } | |
1807 | } | |
1808 | ||
7cac9316 XL |
1809 | #[stable(feature = "herd_cows", since = "1.19.0")] |
1810 | impl<'a> FromIterator<Cow<'a, str>> for String { | |
1811 | fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String { | |
0731742a XL |
1812 | let mut iterator = iter.into_iter(); |
1813 | ||
1814 | // Because we're iterating over CoWs, we can (potentially) avoid at least | |
1815 | // one allocation by getting the first item and appending to it all the | |
1816 | // subsequent items. | |
1817 | match iterator.next() { | |
1818 | None => String::new(), | |
1819 | Some(cow) => { | |
1820 | let mut buf = cow.into_owned(); | |
1821 | buf.extend(iterator); | |
1822 | buf | |
1823 | } | |
1824 | } | |
7cac9316 XL |
1825 | } |
1826 | } | |
1827 | ||
bd371182 | 1828 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1829 | impl Extend<char> for String { |
54a0048b SL |
1830 | fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) { |
1831 | let iterator = iter.into_iter(); | |
1a4d82fc JJ |
1832 | let (lower_bound, _) = iterator.size_hint(); |
1833 | self.reserve(lower_bound); | |
0731742a | 1834 | iterator.for_each(move |c| self.push(c)); |
1a4d82fc | 1835 | } |
f9f354fc XL |
1836 | |
1837 | #[inline] | |
1838 | fn extend_one(&mut self, c: char) { | |
1839 | self.push(c); | |
1840 | } | |
1841 | ||
1842 | #[inline] | |
1843 | fn extend_reserve(&mut self, additional: usize) { | |
1844 | self.reserve(additional); | |
1845 | } | |
1a4d82fc JJ |
1846 | } |
1847 | ||
62682a34 SL |
1848 | #[stable(feature = "extend_ref", since = "1.2.0")] |
1849 | impl<'a> Extend<&'a char> for String { | |
54a0048b SL |
1850 | fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) { |
1851 | self.extend(iter.into_iter().cloned()); | |
62682a34 | 1852 | } |
f9f354fc XL |
1853 | |
1854 | #[inline] | |
1855 | fn extend_one(&mut self, &c: &'a char) { | |
1856 | self.push(c); | |
1857 | } | |
1858 | ||
1859 | #[inline] | |
1860 | fn extend_reserve(&mut self, additional: usize) { | |
1861 | self.reserve(additional); | |
1862 | } | |
62682a34 SL |
1863 | } |
1864 | ||
bd371182 | 1865 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1866 | impl<'a> Extend<&'a str> for String { |
54a0048b | 1867 | fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) { |
0731742a | 1868 | iter.into_iter().for_each(move |s| self.push_str(s)); |
1a4d82fc | 1869 | } |
f9f354fc XL |
1870 | |
1871 | #[inline] | |
1872 | fn extend_one(&mut self, s: &'a str) { | |
1873 | self.push_str(s); | |
1874 | } | |
1a4d82fc JJ |
1875 | } |
1876 | ||
f035d41b XL |
1877 | #[stable(feature = "box_str2", since = "1.45.0")] |
1878 | impl Extend<Box<str>> for String { | |
1879 | fn extend<I: IntoIterator<Item = Box<str>>>(&mut self, iter: I) { | |
1880 | iter.into_iter().for_each(move |s| self.push_str(&s)); | |
1881 | } | |
1882 | } | |
1883 | ||
e9174d1e SL |
1884 | #[stable(feature = "extend_string", since = "1.4.0")] |
1885 | impl Extend<String> for String { | |
54a0048b | 1886 | fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) { |
0731742a | 1887 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
e9174d1e | 1888 | } |
f9f354fc XL |
1889 | |
1890 | #[inline] | |
1891 | fn extend_one(&mut self, s: String) { | |
1892 | self.push_str(&s); | |
1893 | } | |
e9174d1e SL |
1894 | } |
1895 | ||
7cac9316 XL |
1896 | #[stable(feature = "herd_cows", since = "1.19.0")] |
1897 | impl<'a> Extend<Cow<'a, str>> for String { | |
1898 | fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) { | |
0731742a | 1899 | iter.into_iter().for_each(move |s| self.push_str(&s)); |
7cac9316 | 1900 | } |
f9f354fc XL |
1901 | |
1902 | #[inline] | |
1903 | fn extend_one(&mut self, s: Cow<'a, str>) { | |
1904 | self.push_str(&s); | |
1905 | } | |
7cac9316 XL |
1906 | } |
1907 | ||
ba9703b0 XL |
1908 | /// A convenience impl that delegates to the impl for `&str`. |
1909 | /// | |
1910 | /// # Examples | |
1911 | /// | |
1912 | /// ``` | |
1913 | /// assert_eq!(String::from("Hello world").find("world"), Some(6)); | |
1914 | /// ``` | |
dfeec247 XL |
1915 | #[unstable( |
1916 | feature = "pattern", | |
1917 | reason = "API not fully fleshed out and ready to be stabilized", | |
1918 | issue = "27721" | |
1919 | )] | |
c34b1796 AL |
1920 | impl<'a, 'b> Pattern<'a> for &'b String { |
1921 | type Searcher = <&'b str as Pattern<'a>>::Searcher; | |
1922 | ||
1923 | fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher { | |
1924 | self[..].into_searcher(haystack) | |
1925 | } | |
1926 | ||
1927 | #[inline] | |
1928 | fn is_contained_in(self, haystack: &'a str) -> bool { | |
1929 | self[..].is_contained_in(haystack) | |
1930 | } | |
1931 | ||
1932 | #[inline] | |
1933 | fn is_prefix_of(self, haystack: &'a str) -> bool { | |
1934 | self[..].is_prefix_of(haystack) | |
1935 | } | |
ba9703b0 XL |
1936 | |
1937 | #[inline] | |
1938 | fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> { | |
1939 | self[..].strip_prefix_of(haystack) | |
1940 | } | |
1941 | ||
1942 | #[inline] | |
1943 | fn is_suffix_of(self, haystack: &'a str) -> bool { | |
1944 | self[..].is_suffix_of(haystack) | |
1945 | } | |
1946 | ||
1947 | #[inline] | |
1948 | fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> { | |
1949 | self[..].strip_suffix_of(haystack) | |
1950 | } | |
c34b1796 AL |
1951 | } |
1952 | ||
85aaf69f | 1953 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1954 | impl PartialEq for String { |
1955 | #[inline] | |
92a42be0 SL |
1956 | fn eq(&self, other: &String) -> bool { |
1957 | PartialEq::eq(&self[..], &other[..]) | |
1958 | } | |
1a4d82fc | 1959 | #[inline] |
92a42be0 SL |
1960 | fn ne(&self, other: &String) -> bool { |
1961 | PartialEq::ne(&self[..], &other[..]) | |
1962 | } | |
1a4d82fc JJ |
1963 | } |
1964 | ||
1965 | macro_rules! impl_eq { | |
1966 | ($lhs:ty, $rhs: ty) => { | |
85aaf69f | 1967 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 1968 | #[allow(unused_lifetimes)] |
92a42be0 | 1969 | impl<'a, 'b> PartialEq<$rhs> for $lhs { |
1a4d82fc | 1970 | #[inline] |
dfeec247 XL |
1971 | fn eq(&self, other: &$rhs) -> bool { |
1972 | PartialEq::eq(&self[..], &other[..]) | |
1973 | } | |
1a4d82fc | 1974 | #[inline] |
dfeec247 XL |
1975 | fn ne(&self, other: &$rhs) -> bool { |
1976 | PartialEq::ne(&self[..], &other[..]) | |
1977 | } | |
1a4d82fc JJ |
1978 | } |
1979 | ||
85aaf69f | 1980 | #[stable(feature = "rust1", since = "1.0.0")] |
416331ca | 1981 | #[allow(unused_lifetimes)] |
92a42be0 | 1982 | impl<'a, 'b> PartialEq<$lhs> for $rhs { |
1a4d82fc | 1983 | #[inline] |
dfeec247 XL |
1984 | fn eq(&self, other: &$lhs) -> bool { |
1985 | PartialEq::eq(&self[..], &other[..]) | |
1986 | } | |
1a4d82fc | 1987 | #[inline] |
dfeec247 XL |
1988 | fn ne(&self, other: &$lhs) -> bool { |
1989 | PartialEq::ne(&self[..], &other[..]) | |
1990 | } | |
1a4d82fc | 1991 | } |
dfeec247 | 1992 | }; |
1a4d82fc JJ |
1993 | } |
1994 | ||
9346a6ac | 1995 | impl_eq! { String, str } |
1a4d82fc | 1996 | impl_eq! { String, &'a str } |
9346a6ac | 1997 | impl_eq! { Cow<'a, str>, str } |
92a42be0 | 1998 | impl_eq! { Cow<'a, str>, &'b str } |
85aaf69f | 1999 | impl_eq! { Cow<'a, str>, String } |
1a4d82fc | 2000 | |
85aaf69f | 2001 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 2002 | impl Default for String { |
9e0c209e | 2003 | /// Creates an empty `String`. |
85aaf69f | 2004 | #[inline] |
1a4d82fc JJ |
2005 | fn default() -> String { |
2006 | String::new() | |
2007 | } | |
2008 | } | |
2009 | ||
85aaf69f SL |
2010 | #[stable(feature = "rust1", since = "1.0.0")] |
2011 | impl fmt::Display for String { | |
2012 | #[inline] | |
9fa01778 | 2013 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 2014 | fmt::Display::fmt(&**self, f) |
1a4d82fc JJ |
2015 | } |
2016 | } | |
2017 | ||
85aaf69f SL |
2018 | #[stable(feature = "rust1", since = "1.0.0")] |
2019 | impl fmt::Debug for String { | |
2020 | #[inline] | |
9fa01778 | 2021 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
85aaf69f | 2022 | fmt::Debug::fmt(&**self, f) |
1a4d82fc JJ |
2023 | } |
2024 | } | |
2025 | ||
85aaf69f | 2026 | #[stable(feature = "rust1", since = "1.0.0")] |
85aaf69f | 2027 | impl hash::Hash for String { |
1a4d82fc | 2028 | #[inline] |
85aaf69f | 2029 | fn hash<H: hash::Hasher>(&self, hasher: &mut H) { |
1a4d82fc JJ |
2030 | (**self).hash(hasher) |
2031 | } | |
2032 | } | |
2033 | ||
8bb4bdeb XL |
2034 | /// Implements the `+` operator for concatenating two strings. |
2035 | /// | |
2036 | /// This consumes the `String` on the left-hand side and re-uses its buffer (growing it if | |
2037 | /// necessary). This is done to avoid allocating a new `String` and copying the entire contents on | |
3dfed10e | 2038 | /// every operation, which would lead to *O*(*n*^2) running time when building an *n*-byte string by |
8bb4bdeb XL |
2039 | /// repeated concatenation. |
2040 | /// | |
2041 | /// The string on the right-hand side is only borrowed; its contents are copied into the returned | |
2042 | /// `String`. | |
2043 | /// | |
2044 | /// # Examples | |
2045 | /// | |
2046 | /// Concatenating two `String`s takes the first by value and borrows the second: | |
2047 | /// | |
2048 | /// ``` | |
2049 | /// let a = String::from("hello"); | |
2050 | /// let b = String::from(" world"); | |
2051 | /// let c = a + &b; | |
2052 | /// // `a` is moved and can no longer be used here. | |
2053 | /// ``` | |
2054 | /// | |
2055 | /// If you want to keep using the first `String`, you can clone it and append to the clone instead: | |
2056 | /// | |
2057 | /// ``` | |
2058 | /// let a = String::from("hello"); | |
2059 | /// let b = String::from(" world"); | |
2060 | /// let c = a.clone() + &b; | |
2061 | /// // `a` is still valid here. | |
2062 | /// ``` | |
2063 | /// | |
2064 | /// Concatenating `&str` slices can be done by converting the first to a `String`: | |
2065 | /// | |
2066 | /// ``` | |
2067 | /// let a = "hello"; | |
2068 | /// let b = " world"; | |
2069 | /// let c = a.to_string() + b; | |
2070 | /// ``` | |
bd371182 | 2071 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 | 2072 | impl Add<&str> for String { |
1a4d82fc JJ |
2073 | type Output = String; |
2074 | ||
85aaf69f | 2075 | #[inline] |
1a4d82fc JJ |
2076 | fn add(mut self, other: &str) -> String { |
2077 | self.push_str(other); | |
2078 | self | |
2079 | } | |
2080 | } | |
2081 | ||
8bb4bdeb XL |
2082 | /// Implements the `+=` operator for appending to a `String`. |
2083 | /// | |
b7449926 | 2084 | /// This has the same behavior as the [`push_str`][String::push_str] method. |
5bcae85e | 2085 | #[stable(feature = "stringaddassign", since = "1.12.0")] |
9fa01778 | 2086 | impl AddAssign<&str> for String { |
5bcae85e SL |
2087 | #[inline] |
2088 | fn add_assign(&mut self, other: &str) { | |
2089 | self.push_str(other); | |
2090 | } | |
2091 | } | |
2092 | ||
85aaf69f SL |
2093 | #[stable(feature = "rust1", since = "1.0.0")] |
2094 | impl ops::Index<ops::Range<usize>> for String { | |
1a4d82fc | 2095 | type Output = str; |
c34b1796 | 2096 | |
1a4d82fc | 2097 | #[inline] |
c34b1796 AL |
2098 | fn index(&self, index: ops::Range<usize>) -> &str { |
2099 | &self[..][index] | |
1a4d82fc JJ |
2100 | } |
2101 | } | |
85aaf69f SL |
2102 | #[stable(feature = "rust1", since = "1.0.0")] |
2103 | impl ops::Index<ops::RangeTo<usize>> for String { | |
1a4d82fc | 2104 | type Output = str; |
c34b1796 | 2105 | |
1a4d82fc | 2106 | #[inline] |
c34b1796 AL |
2107 | fn index(&self, index: ops::RangeTo<usize>) -> &str { |
2108 | &self[..][index] | |
1a4d82fc JJ |
2109 | } |
2110 | } | |
85aaf69f SL |
2111 | #[stable(feature = "rust1", since = "1.0.0")] |
2112 | impl ops::Index<ops::RangeFrom<usize>> for String { | |
1a4d82fc | 2113 | type Output = str; |
c34b1796 | 2114 | |
1a4d82fc | 2115 | #[inline] |
c34b1796 AL |
2116 | fn index(&self, index: ops::RangeFrom<usize>) -> &str { |
2117 | &self[..][index] | |
1a4d82fc JJ |
2118 | } |
2119 | } | |
85aaf69f SL |
2120 | #[stable(feature = "rust1", since = "1.0.0")] |
2121 | impl ops::Index<ops::RangeFull> for String { | |
1a4d82fc | 2122 | type Output = str; |
c34b1796 | 2123 | |
1a4d82fc | 2124 | #[inline] |
c34b1796 | 2125 | fn index(&self, _index: ops::RangeFull) -> &str { |
e9174d1e | 2126 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2127 | } |
2128 | } | |
0531ce1d | 2129 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2130 | impl ops::Index<ops::RangeInclusive<usize>> for String { |
2131 | type Output = str; | |
2132 | ||
2133 | #[inline] | |
2134 | fn index(&self, index: ops::RangeInclusive<usize>) -> &str { | |
2135 | Index::index(&**self, index) | |
2136 | } | |
2137 | } | |
0531ce1d | 2138 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2139 | impl ops::Index<ops::RangeToInclusive<usize>> for String { |
2140 | type Output = str; | |
2141 | ||
2142 | #[inline] | |
2143 | fn index(&self, index: ops::RangeToInclusive<usize>) -> &str { | |
2144 | Index::index(&**self, index) | |
2145 | } | |
2146 | } | |
1a4d82fc | 2147 | |
7cac9316 | 2148 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2149 | impl ops::IndexMut<ops::Range<usize>> for String { |
2150 | #[inline] | |
2151 | fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str { | |
2152 | &mut self[..][index] | |
2153 | } | |
2154 | } | |
7cac9316 | 2155 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2156 | impl ops::IndexMut<ops::RangeTo<usize>> for String { |
2157 | #[inline] | |
2158 | fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str { | |
2159 | &mut self[..][index] | |
2160 | } | |
2161 | } | |
7cac9316 | 2162 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2163 | impl ops::IndexMut<ops::RangeFrom<usize>> for String { |
2164 | #[inline] | |
2165 | fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str { | |
2166 | &mut self[..][index] | |
2167 | } | |
2168 | } | |
7cac9316 | 2169 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d SL |
2170 | impl ops::IndexMut<ops::RangeFull> for String { |
2171 | #[inline] | |
2172 | fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str { | |
cc61c64b | 2173 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
c1a9b12d SL |
2174 | } |
2175 | } | |
0531ce1d | 2176 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2177 | impl ops::IndexMut<ops::RangeInclusive<usize>> for String { |
2178 | #[inline] | |
2179 | fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str { | |
2180 | IndexMut::index_mut(&mut **self, index) | |
2181 | } | |
2182 | } | |
0531ce1d | 2183 | #[stable(feature = "inclusive_range", since = "1.26.0")] |
54a0048b SL |
2184 | impl ops::IndexMut<ops::RangeToInclusive<usize>> for String { |
2185 | #[inline] | |
2186 | fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str { | |
2187 | IndexMut::index_mut(&mut **self, index) | |
2188 | } | |
2189 | } | |
c1a9b12d | 2190 | |
85aaf69f | 2191 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2192 | impl ops::Deref for String { |
2193 | type Target = str; | |
2194 | ||
85aaf69f SL |
2195 | #[inline] |
2196 | fn deref(&self) -> &str { | |
e9174d1e | 2197 | unsafe { str::from_utf8_unchecked(&self.vec) } |
1a4d82fc JJ |
2198 | } |
2199 | } | |
2200 | ||
7cac9316 | 2201 | #[stable(feature = "derefmut_for_string", since = "1.3.0")] |
c1a9b12d | 2202 | impl ops::DerefMut for String { |
85aaf69f | 2203 | #[inline] |
c1a9b12d | 2204 | fn deref_mut(&mut self) -> &mut str { |
cc61c64b | 2205 | unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) } |
1a4d82fc JJ |
2206 | } |
2207 | } | |
2208 | ||
74b04a01 | 2209 | /// A type alias for [`Infallible`]. |
92a42be0 | 2210 | /// |
74b04a01 | 2211 | /// This alias exists for backwards compatibility, and may be eventually deprecated. |
92a42be0 | 2212 | /// |
3dfed10e | 2213 | /// [`Infallible`]: core::convert::Infallible |
b039eaaf | 2214 | #[stable(feature = "str_parse_error", since = "1.5.0")] |
9fa01778 | 2215 | pub type ParseError = core::convert::Infallible; |
bd371182 AL |
2216 | |
2217 | #[stable(feature = "rust1", since = "1.0.0")] | |
1a4d82fc | 2218 | impl FromStr for String { |
9fa01778 | 2219 | type Err = core::convert::Infallible; |
1a4d82fc | 2220 | #[inline] |
74b04a01 | 2221 | fn from_str(s: &str) -> Result<String, Self::Err> { |
62682a34 | 2222 | Ok(String::from(s)) |
1a4d82fc JJ |
2223 | } |
2224 | } | |
2225 | ||
92a42be0 SL |
2226 | /// A trait for converting a value to a `String`. |
2227 | /// | |
2228 | /// This trait is automatically implemented for any type which implements the | |
2229 | /// [`Display`] trait. As such, `ToString` shouldn't be implemented directly: | |
2230 | /// [`Display`] should be implemented instead, and you get the `ToString` | |
2231 | /// implementation for free. | |
2232 | /// | |
3dfed10e | 2233 | /// [`Display`]: fmt::Display |
6a06907d | 2234 | #[cfg_attr(not(test), rustc_diagnostic_item = "ToString")] |
85aaf69f | 2235 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 2236 | pub trait ToString { |
92a42be0 SL |
2237 | /// Converts the given value to a `String`. |
2238 | /// | |
2239 | /// # Examples | |
2240 | /// | |
2241 | /// Basic usage: | |
2242 | /// | |
2243 | /// ``` | |
2244 | /// let i = 5; | |
2245 | /// let five = String::from("5"); | |
2246 | /// | |
2247 | /// assert_eq!(five, i.to_string()); | |
2248 | /// ``` | |
2c00a5a8 | 2249 | #[rustc_conversion_suggestion] |
85aaf69f | 2250 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
2251 | fn to_string(&self) -> String; |
2252 | } | |
2253 | ||
8bb4bdeb XL |
2254 | /// # Panics |
2255 | /// | |
2256 | /// In this implementation, the `to_string` method panics | |
2257 | /// if the `Display` implementation returns an error. | |
2258 | /// This indicates an incorrect `Display` implementation | |
2259 | /// since `fmt::Write for String` never returns an error itself. | |
85aaf69f SL |
2260 | #[stable(feature = "rust1", since = "1.0.0")] |
2261 | impl<T: fmt::Display + ?Sized> ToString for T { | |
3dfed10e | 2262 | // A common guideline is to not inline generic functions. However, |
29967ef6 XL |
2263 | // removing `#[inline]` from this method causes non-negligible regressions. |
2264 | // See <https://github.com/rust-lang/rust/pull/74852>, the last attempt | |
2265 | // to try to remove it. | |
85aaf69f | 2266 | #[inline] |
54a0048b | 2267 | default fn to_string(&self) -> String { |
9fa01778 | 2268 | use fmt::Write; |
1a4d82fc | 2269 | let mut buf = String::new(); |
8bb4bdeb | 2270 | buf.write_fmt(format_args!("{}", self)) |
dfeec247 | 2271 | .expect("a Display implementation returned an error unexpectedly"); |
1a4d82fc JJ |
2272 | buf |
2273 | } | |
2274 | } | |
2275 | ||
f035d41b XL |
2276 | #[stable(feature = "char_to_string_specialization", since = "1.46.0")] |
2277 | impl ToString for char { | |
2278 | #[inline] | |
2279 | fn to_string(&self) -> String { | |
2280 | String::from(self.encode_utf8(&mut [0; 4])) | |
2281 | } | |
2282 | } | |
2283 | ||
54a0048b SL |
2284 | #[stable(feature = "str_to_string_specialization", since = "1.9.0")] |
2285 | impl ToString for str { | |
2286 | #[inline] | |
2287 | fn to_string(&self) -> String { | |
2288 | String::from(self) | |
2289 | } | |
2290 | } | |
2291 | ||
8bb4bdeb | 2292 | #[stable(feature = "cow_str_to_string_specialization", since = "1.17.0")] |
9fa01778 | 2293 | impl ToString for Cow<'_, str> { |
8bb4bdeb XL |
2294 | #[inline] |
2295 | fn to_string(&self) -> String { | |
2296 | self[..].to_owned() | |
2297 | } | |
2298 | } | |
2299 | ||
2300 | #[stable(feature = "string_to_string_specialization", since = "1.17.0")] | |
2301 | impl ToString for String { | |
2302 | #[inline] | |
2303 | fn to_string(&self) -> String { | |
2304 | self.to_owned() | |
2305 | } | |
2306 | } | |
2307 | ||
85aaf69f | 2308 | #[stable(feature = "rust1", since = "1.0.0")] |
c34b1796 | 2309 | impl AsRef<str> for String { |
d9579d0f | 2310 | #[inline] |
c34b1796 AL |
2311 | fn as_ref(&self) -> &str { |
2312 | self | |
2313 | } | |
2314 | } | |
2315 | ||
74b04a01 XL |
2316 | #[stable(feature = "string_as_mut", since = "1.43.0")] |
2317 | impl AsMut<str> for String { | |
2318 | #[inline] | |
2319 | fn as_mut(&mut self) -> &mut str { | |
2320 | self | |
2321 | } | |
2322 | } | |
2323 | ||
bd371182 AL |
2324 | #[stable(feature = "rust1", since = "1.0.0")] |
2325 | impl AsRef<[u8]> for String { | |
2326 | #[inline] | |
2327 | fn as_ref(&self) -> &[u8] { | |
2328 | self.as_bytes() | |
2329 | } | |
2330 | } | |
2331 | ||
c34b1796 | 2332 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 2333 | impl From<&str> for String { |
0bf4aa26 | 2334 | #[inline] |
532ac7d7 | 2335 | fn from(s: &str) -> String { |
54a0048b | 2336 | s.to_owned() |
c34b1796 AL |
2337 | } |
2338 | } | |
2339 | ||
ba9703b0 XL |
2340 | #[stable(feature = "from_mut_str_for_string", since = "1.44.0")] |
2341 | impl From<&mut str> for String { | |
2342 | /// Converts a `&mut str` into a `String`. | |
2343 | /// | |
2344 | /// The result is allocated on the heap. | |
2345 | #[inline] | |
2346 | fn from(s: &mut str) -> String { | |
2347 | s.to_owned() | |
2348 | } | |
2349 | } | |
2350 | ||
48663c56 XL |
2351 | #[stable(feature = "from_ref_string", since = "1.35.0")] |
2352 | impl From<&String> for String { | |
2353 | #[inline] | |
2354 | fn from(s: &String) -> String { | |
2355 | s.clone() | |
2356 | } | |
2357 | } | |
2358 | ||
cc61c64b XL |
2359 | // note: test pulls in libstd, which causes errors here |
2360 | #[cfg(not(test))] | |
7cac9316 | 2361 | #[stable(feature = "string_from_box", since = "1.18.0")] |
cc61c64b | 2362 | impl From<Box<str>> for String { |
a1dfa0c6 XL |
2363 | /// Converts the given boxed `str` slice to a `String`. |
2364 | /// It is notable that the `str` slice is owned. | |
2365 | /// | |
2366 | /// # Examples | |
2367 | /// | |
2368 | /// Basic usage: | |
2369 | /// | |
2370 | /// ``` | |
2371 | /// let s1: String = String::from("hello world"); | |
2372 | /// let s2: Box<str> = s1.into_boxed_str(); | |
2373 | /// let s3: String = String::from(s2); | |
2374 | /// | |
2375 | /// assert_eq!("hello world", s3) | |
2376 | /// ``` | |
cc61c64b XL |
2377 | fn from(s: Box<str>) -> String { |
2378 | s.into_string() | |
2379 | } | |
2380 | } | |
2381 | ||
041b39d2 XL |
2382 | #[stable(feature = "box_from_str", since = "1.20.0")] |
2383 | impl From<String> for Box<str> { | |
a1dfa0c6 XL |
2384 | /// Converts the given `String` to a boxed `str` slice that is owned. |
2385 | /// | |
2386 | /// # Examples | |
2387 | /// | |
2388 | /// Basic usage: | |
2389 | /// | |
2390 | /// ``` | |
2391 | /// let s1: String = String::from("hello world"); | |
2392 | /// let s2: Box<str> = Box::from(s1); | |
2393 | /// let s3: String = String::from(s2); | |
2394 | /// | |
2395 | /// assert_eq!("hello world", s3) | |
2396 | /// ``` | |
041b39d2 XL |
2397 | fn from(s: String) -> Box<str> { |
2398 | s.into_boxed_str() | |
cc61c64b XL |
2399 | } |
2400 | } | |
2401 | ||
c30ab7b3 SL |
2402 | #[stable(feature = "string_from_cow_str", since = "1.14.0")] |
2403 | impl<'a> From<Cow<'a, str>> for String { | |
2404 | fn from(s: Cow<'a, str>) -> String { | |
2405 | s.into_owned() | |
2406 | } | |
2407 | } | |
2408 | ||
c34b1796 AL |
2409 | #[stable(feature = "rust1", since = "1.0.0")] |
2410 | impl<'a> From<&'a str> for Cow<'a, str> { | |
6a06907d XL |
2411 | /// Converts a string slice into a Borrowed variant. |
2412 | /// No heap allocation is performed, and the string | |
2413 | /// is not copied. | |
2414 | /// | |
2415 | /// # Example | |
2416 | /// | |
2417 | /// ``` | |
2418 | /// # use std::borrow::Cow; | |
2419 | /// assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant")); | |
2420 | /// ``` | |
c34b1796 AL |
2421 | #[inline] |
2422 | fn from(s: &'a str) -> Cow<'a, str> { | |
2423 | Cow::Borrowed(s) | |
2424 | } | |
2425 | } | |
2426 | ||
2427 | #[stable(feature = "rust1", since = "1.0.0")] | |
2428 | impl<'a> From<String> for Cow<'a, str> { | |
6a06907d XL |
2429 | /// Converts a String into an Owned variant. |
2430 | /// No heap allocation is performed, and the string | |
2431 | /// is not copied. | |
2432 | /// | |
2433 | /// # Example | |
2434 | /// | |
2435 | /// ``` | |
2436 | /// # use std::borrow::Cow; | |
2437 | /// let s = "eggplant".to_string(); | |
2438 | /// let s2 = "eggplant".to_string(); | |
2439 | /// assert_eq!(Cow::from(s), Cow::<'static, str>::Owned(s2)); | |
2440 | /// ``` | |
c34b1796 AL |
2441 | #[inline] |
2442 | fn from(s: String) -> Cow<'a, str> { | |
2443 | Cow::Owned(s) | |
2444 | } | |
2445 | } | |
2446 | ||
94b46f34 XL |
2447 | #[stable(feature = "cow_from_string_ref", since = "1.28.0")] |
2448 | impl<'a> From<&'a String> for Cow<'a, str> { | |
6a06907d XL |
2449 | /// Converts a String reference into a Borrowed variant. |
2450 | /// No heap allocation is performed, and the string | |
2451 | /// is not copied. | |
2452 | /// | |
2453 | /// # Example | |
2454 | /// | |
2455 | /// ``` | |
2456 | /// # use std::borrow::Cow; | |
2457 | /// let s = "eggplant".to_string(); | |
2458 | /// assert_eq!(Cow::from(&s), Cow::Borrowed("eggplant")); | |
2459 | /// ``` | |
94b46f34 XL |
2460 | #[inline] |
2461 | fn from(s: &'a String) -> Cow<'a, str> { | |
2462 | Cow::Borrowed(s.as_str()) | |
2463 | } | |
2464 | } | |
2465 | ||
5bcae85e SL |
2466 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] |
2467 | impl<'a> FromIterator<char> for Cow<'a, str> { | |
2468 | fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> { | |
2469 | Cow::Owned(FromIterator::from_iter(it)) | |
2470 | } | |
2471 | } | |
2472 | ||
2473 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] | |
2474 | impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str> { | |
2475 | fn from_iter<I: IntoIterator<Item = &'b str>>(it: I) -> Cow<'a, str> { | |
2476 | Cow::Owned(FromIterator::from_iter(it)) | |
2477 | } | |
2478 | } | |
2479 | ||
2480 | #[stable(feature = "cow_str_from_iter", since = "1.12.0")] | |
2481 | impl<'a> FromIterator<String> for Cow<'a, str> { | |
2482 | fn from_iter<I: IntoIterator<Item = String>>(it: I) -> Cow<'a, str> { | |
2483 | Cow::Owned(FromIterator::from_iter(it)) | |
2484 | } | |
2485 | } | |
2486 | ||
c30ab7b3 SL |
2487 | #[stable(feature = "from_string_for_vec_u8", since = "1.14.0")] |
2488 | impl From<String> for Vec<u8> { | |
a1dfa0c6 XL |
2489 | /// Converts the given `String` to a vector `Vec` that holds values of type `u8`. |
2490 | /// | |
2491 | /// # Examples | |
2492 | /// | |
2493 | /// Basic usage: | |
2494 | /// | |
2495 | /// ``` | |
2496 | /// let s1 = String::from("hello world"); | |
2497 | /// let v1 = Vec::from(s1); | |
2498 | /// | |
2499 | /// for b in v1 { | |
2500 | /// println!("{}", b); | |
2501 | /// } | |
2502 | /// ``` | |
32a655c1 | 2503 | fn from(string: String) -> Vec<u8> { |
c30ab7b3 | 2504 | string.into_bytes() |
c34b1796 AL |
2505 | } |
2506 | } | |
2507 | ||
85aaf69f SL |
2508 | #[stable(feature = "rust1", since = "1.0.0")] |
2509 | impl fmt::Write for String { | |
2510 | #[inline] | |
1a4d82fc JJ |
2511 | fn write_str(&mut self, s: &str) -> fmt::Result { |
2512 | self.push_str(s); | |
2513 | Ok(()) | |
2514 | } | |
d9579d0f AL |
2515 | |
2516 | #[inline] | |
2517 | fn write_char(&mut self, c: char) -> fmt::Result { | |
2518 | self.push(c); | |
2519 | Ok(()) | |
2520 | } | |
2521 | } | |
2522 | ||
2523 | /// A draining iterator for `String`. | |
7453a54e | 2524 | /// |
cc61c64b | 2525 | /// This struct is created by the [`drain`] method on [`String`]. See its |
7453a54e SL |
2526 | /// documentation for more. |
2527 | /// | |
3dfed10e | 2528 | /// [`drain`]: String::drain |
92a42be0 | 2529 | #[stable(feature = "drain", since = "1.6.0")] |
d9579d0f AL |
2530 | pub struct Drain<'a> { |
2531 | /// Will be used as &'a mut String in the destructor | |
2532 | string: *mut String, | |
2533 | /// Start of part to remove | |
2534 | start: usize, | |
2535 | /// End of part to remove | |
2536 | end: usize, | |
2537 | /// Current remaining range to remove | |
2538 | iter: Chars<'a>, | |
2539 | } | |
2540 | ||
8bb4bdeb | 2541 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
2542 | impl fmt::Debug for Drain<'_> { |
2543 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
1b1a35ee | 2544 | f.debug_tuple("Drain").field(&self.as_str()).finish() |
8bb4bdeb XL |
2545 | } |
2546 | } | |
2547 | ||
92a42be0 | 2548 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2549 | unsafe impl Sync for Drain<'_> {} |
92a42be0 | 2550 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2551 | unsafe impl Send for Drain<'_> {} |
d9579d0f | 2552 | |
92a42be0 | 2553 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2554 | impl Drop for Drain<'_> { |
d9579d0f AL |
2555 | fn drop(&mut self) { |
2556 | unsafe { | |
2557 | // Use Vec::drain. "Reaffirm" the bounds checks to avoid | |
2558 | // panic code being inserted again. | |
2559 | let self_vec = (*self.string).as_mut_vec(); | |
2560 | if self.start <= self.end && self.end <= self_vec.len() { | |
2561 | self_vec.drain(self.start..self.end); | |
2562 | } | |
2563 | } | |
2564 | } | |
2565 | } | |
2566 | ||
1b1a35ee XL |
2567 | impl<'a> Drain<'a> { |
2568 | /// Returns the remaining (sub)string of this iterator as a slice. | |
2569 | /// | |
2570 | /// # Examples | |
2571 | /// | |
2572 | /// ``` | |
2573 | /// #![feature(string_drain_as_str)] | |
2574 | /// let mut s = String::from("abc"); | |
2575 | /// let mut drain = s.drain(..); | |
2576 | /// assert_eq!(drain.as_str(), "abc"); | |
2577 | /// let _ = drain.next().unwrap(); | |
2578 | /// assert_eq!(drain.as_str(), "bc"); | |
2579 | /// ``` | |
2580 | #[unstable(feature = "string_drain_as_str", issue = "76905")] // Note: uncomment AsRef impls below when stabilizing. | |
2581 | pub fn as_str(&self) -> &str { | |
2582 | self.iter.as_str() | |
2583 | } | |
2584 | } | |
2585 | ||
2586 | // Uncomment when stabilizing `string_drain_as_str`. | |
2587 | // #[unstable(feature = "string_drain_as_str", issue = "76905")] | |
2588 | // impl<'a> AsRef<str> for Drain<'a> { | |
2589 | // fn as_ref(&self) -> &str { | |
2590 | // self.as_str() | |
2591 | // } | |
2592 | // } | |
2593 | // | |
2594 | // #[unstable(feature = "string_drain_as_str", issue = "76905")] | |
2595 | // impl<'a> AsRef<[u8]> for Drain<'a> { | |
2596 | // fn as_ref(&self) -> &[u8] { | |
2597 | // self.as_str().as_bytes() | |
2598 | // } | |
2599 | // } | |
2600 | ||
92a42be0 | 2601 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2602 | impl Iterator for Drain<'_> { |
d9579d0f AL |
2603 | type Item = char; |
2604 | ||
2605 | #[inline] | |
2606 | fn next(&mut self) -> Option<char> { | |
2607 | self.iter.next() | |
2608 | } | |
2609 | ||
2610 | fn size_hint(&self) -> (usize, Option<usize>) { | |
2611 | self.iter.size_hint() | |
2612 | } | |
416331ca XL |
2613 | |
2614 | #[inline] | |
2615 | fn last(mut self) -> Option<char> { | |
2616 | self.next_back() | |
2617 | } | |
d9579d0f AL |
2618 | } |
2619 | ||
92a42be0 | 2620 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 2621 | impl DoubleEndedIterator for Drain<'_> { |
d9579d0f AL |
2622 | #[inline] |
2623 | fn next_back(&mut self) -> Option<char> { | |
2624 | self.iter.next_back() | |
2625 | } | |
1a4d82fc | 2626 | } |
9e0c209e | 2627 | |
0531ce1d | 2628 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 2629 | impl FusedIterator for Drain<'_> {} |
f035d41b XL |
2630 | |
2631 | #[stable(feature = "from_char_for_string", since = "1.46.0")] | |
2632 | impl From<char> for String { | |
2633 | #[inline] | |
2634 | fn from(c: char) -> Self { | |
2635 | c.to_string() | |
2636 | } | |
2637 | } |